The Southern Ocean Observing System: Initial Science and ... · Southern Ocean and its role in the...

1

The Southern Ocean Observing System: 2

Initial Science and Implementation Strategy 3

4

Draft for review and community comment 5

6

August 2010 7

8 Edited by: 9 Stephen R. Rintoul, CSIRO and Antarctic Climate and Ecosystems Cooperative 10

Research Centre, Australia 11 Mike Sparrow, Scientific Committee on Antarctic Research, UK 12 Mike Meredith, British Antarctic Survey, UK 13 Victoria Wadley, Australian Antarctic Division, Aus 14 Kevin Speer, Florida State University, USA 15 Eileen Hoffman, Old Dominion University, USA 16 Colin Summerhayes, UK 17 Ed Urban, Scientific Committee on Oceanic Research, USA 18

19

20 Contributors: Albert Fischer, Alberto Naveira Garabato, Christian Haas, Claude de 21 Broyer, Colin Southwell, Dan Costa, Damia Gomis, Dave Carlson, Detlef Stammer, 22 Eberhard Fahrbach, Ed Sarukhanian, Edith Fanta, Eric Rignot, Etienne Charpentier, 23 Eugene Murphy, Graham Hosie, Hartwig Gernandt, Hein De Baar, Hyoung Chul 24 Shin, Isabelle Ansorge, Jill Schwarz, John Gunn, Julian Gutt, Julie Hall, Karen 25 Haywood, Kate Stansfield, Keith Alverson, Lars Boehme, Lars Kaleschke, Lucia 26 Campos, Mario Hoppema, Mark Hindell, Mathieu Belbeoch, Matthew England, 27 Meghan Cronin, Mike Fedak, Monica Muelbert, Norbert Ott, Pierre-Philipe Mathieu, 28 Richard Bellerby, Sabrina Speich, Sergei Gladyshev, Shigeru Aoki, Simon Wright, 29 Steve Ackley, Steve Piotrowicz, Steven Nichol, Sung-Ho Kang, Taco de Bruin, Tony 30 Worby, Victoria Lytle, Vladimir Ryabinin, Werner Stambach, William Howard 31 32 33

34

35 36 37 38 39 40 41 42 43 44

SOOS Draft for Review (August 1 2010)

1

TABLE OF CONTENTS 45

TABLEOFCONTENTS .......................................................................................................1 46

ExecutiveSummary ..........................................................................................................2 47

1.Introduction...................................................................................................................4 48 1.1TheSouthernOceananditsroleintheEarthSystem..................................................... 4 49 1.2ObservedchangesintheSouthernOcean............................................................................ 5 50 1.3TheneedforasustainedSouthernOceanObservingSystem ..................................... 6 51 1.4AVisionforaSouthernOceanObservingSystem ............................................................ 8 52 1.5Purposeandstructureofthestrategy ................................................................................... 8 53

2.RationaleforaSouthernOceanObservingSystem ...........................................9 54 2.1RoleoftheSouthernOceaninclimateandglobalbiogeochemicalcycles ............. 9 55 2.2Seaiceandiceshelves ................................................................................................................12 56 2.3SouthernOceanbiologyandecology ...................................................................................16 57 2.4ObservedChangesintheSouthernOcean .........................................................................20 58 2.5InformingDecision‐makers......................................................................................................30 59

3.DesignofaSouthernOceanObservingSystem................................................ 30 60 3.1Keysciencechallengesandtheneedforsustainedobservations ...........................30 61 3.2BuildingblocksofanintegratedSouthernOceanObservingSystem....................32 62 3.3Complementaryresearch ..........................................................................................................55 63

4.StatusandaroadmapforimplementationofSOOS ...................................... 57 64 4.1SOOSasalegacyoftheInternationalPolarYear ............................................................57 65 4.2StatusofSouthernOceanobservations...............................................................................57 66 4.3Nextstepstowardsimplementation ....................................................................................59 67 4.4Datastrategy...................................................................................................................................64 68 4.5SOOSin10years............................................................................................................................65 69

5.Conclusion ................................................................................................................... 66 70

Acronyms: ......................................................................................................................... 67 71

References ........................................................................................................................ 68 72

73

Rosemary Nash � 26/7/10 14:09Deleted: 63


2

Executive Summary 73

74 The Southern Ocean provides the principal connection between the Earth’s ocean 75 basins and between the upper and lower layers of the global ocean circulation. As a 76 result, the Southern Ocean strongly influences climate patterns and the cycling of 77 carbon and nutrients. Changes in the Southern Ocean would therefore have global 78 ramifications. 79 80 Limited observations suggest the Southern Ocean is indeed changing: the region is 81 warming more rapidly than the global ocean average; salinity changes driven by 82 changes in precipitation and ice melt have been observed in both the upper and 83 abyssal ocean; the uptake of carbon by the Southern Ocean has slowed the rate of 84 climate change but increased the acidity of the ocean; and Southern Ocean ecosystems 85 are reacting to changes in the physical and chemical environment. 86 87 However, the short and incomplete nature of existing time series makes the causes 88 and consequences of observed changes difficult to assess. Sustained, multi-89 disciplinary observations are required to detect, interpret and respond to change. 90 91 The Southern Ocean Observing System (SOOS) is motivated by the need to address 92 six key challenges in Southern Ocean science: 93

1. The role of the Southern Ocean in the planet’s heat and freshwater balance 94 2. The stability of the Southern Ocean overturning circulation 95 3. The role of the ocean in the stability of the Antarctic ice sheet and its 96 contribution to sea-level rise 97 4. The future and consequences of Southern Ocean carbon uptake 98 5. The future of Antarctic sea ice 99 6. The impacts of global change on Southern Ocean ecosystems 100

101 There is an urgent and compelling need to make progress in each of these areas to 102 inform decision-makers confronted with the challenges of climate change, sea-level 103 rise, ocean acidification, and the sustainable management of marine resources. To 104 deliver this information, sustained observations of the physical, biogeochemical and 105 biological state of the Southern Ocean are critical. 106 107 The lack of historical observations has slowed progress in understanding the Southern 108 Ocean and its connections to the rest of the Earth system. However, advances in 109 technology and knowledge mean that it is now possible to design and implement a 110 sustained, feasible and cost-effective observing system for this remote environment. 111 112 Users of the SOOS will include the research community, managers of marine 113 resources, policy makers, local planners, shipping operators, Antarctic tourism 114 operators, weather and climate forecasters, and educators. A number of international 115 organisations, including the International Oceanographic Commission of UNESCO, 116 the World Meteorological Organisation and the Scientific Committee on Antarctic 117 Research, have noted the need for sustained observations of the Southern Ocean and 118 supported the development of the SOOS. 119 120 This document outlines the scientific rationale and strategy for the SOOS; identifies 121 the variables to be observed; presents a draft plan for an integrated multi-disciplinary 122


3

observing system for the Southern Ocean; and identifies the next steps required for 123 implementation. 124 125

126


4

1. Introduction 126

1.1TheSouthernOceananditsroleintheEarthSystem127

128 As a result of the unique geography of the Southern Ocean, the region has a profound 129 influence on the global ocean circulation and the Earth’s climate. The absence of land 130 barriers in the latitude band of Drake Passage allows a circumpolar current to exist. 131 The Antarctic Circumpolar Current (ACC) is the largest current in the world ocean 132 and, by connecting the ocean basins, exerts a major influence on global climate. The 133 existence of the ACC tends to restrict the poleward transport of heat, in contrast to the 134 northern hemisphere where currents transport heat directly to high latitudes. The 135 strong north-south tilt of density surfaces associated with the eastward flow of the 136 ACC exposes the deep layers of the ocean to the atmosphere at high southern 137 latitudes. Wind and buoyancy forcing at these isopycnal outcrops transfers water 138 between density layers, and connects the deep global ocean to the surface layers. In 139 this way, the Southern Ocean controls the connection between the deep and upper 140 layers of the global overturning circulation and thereby regulates the capacity of the 141 ocean to store and transport heat, carbon and other properties that influence climate 142 and global biogeochemical cycles (e.g. Rintoul et al., 2001). 143 144 The upwelling branch of the overturning circulation in the Southern Ocean returns 145 carbon and nutrients to the surface layer, while the downwelling branches transport 146 heat, carbon and other properties into the ocean interior. The balance between 147 upwelling and outgassing versus subduction of carbon into the ocean interior 148 determines the strength of the Southern Ocean sink of CO2. This balance depends on 149 the wind forcing and eddy dynamics of the ACC. The Southern Ocean contributes 150 more to the ocean storage of the excess heat and carbon added to the Earth-151 atmosphere system by human activities than any other latitudinal band (Levitus et al., 152 2005; Sabine et al., 2004). About 40% of the total global ocean inventory of 153 anthropogenic carbon dioxide is found south of 30°S (Sabine et al., 2004). Export of 154 nutrients by the upper limb of the overturning circulation ultimately supports 75% of 155 the global ocean primary production north of 30°S (Sarmiento et al., 2004). 156 157 Climate and sea-level rise are influenced strongly by ocean-cryosphere interactions in 158 the Southern Ocean. Changes in sea ice extent or volume result in changes in the 159 Earth’s albedo, oceanic water mass formation rates, air-sea exchange of gases such as 160 carbon dioxide, and affect oceanic organisms from microbes to whales in terms of 161 physiological changes and changes to their habitats. Melting of floating glacial ice by 162 warm ocean waters influences the high latitude freshwater budget and stratification 163 and may affect the stability of the Antarctic ice sheet and the rate at which glacial ice 164 flows to the sea. 165 166 Given the influence of the Southern Ocean, any changes in the region would have 167 global consequences. In particular, coupling between ocean circulation, sea ice and 168 biogeochemical cycles can result in positive feedbacks that drive further climate 169 change. Changes to the freshwater balance as a result of changes in sea ice, 170 precipitation, or ocean-ice shelf interaction may influence the strength of the 171 overturning circulation. Reductions in sea ice extent will drive further warming by 172


5

reducing the ice-albedo feedback. Models suggest that the ability of the Southern 173 Ocean to absorb carbon dioxide will decline as climate change progresses, providing 174 another positive feedback (Sarmiento et al., 2004; Le Quere et al., 2007). Turner et 175 al. (2009a) provide a comprehensive review of the role of Antarctica and the Southern 176 Ocean in the global system and the potential sensitivity to change (see also Mayewski 177 et al., 2009, and Convey et al, 2009). 178 179 Here we adopt the standard oceanographic definition of the Southern Ocean as the 180 waters between the Subtropical Front and the Antarctic continent. This is a broader 181 definition than used in some policy contexts, but reflects the circumpolar continuity of 182 the waters of this oceanic domain, and the strong scientific connections between them. 183 184

1.2ObservedchangesintheSouthernOcean185

186 Changes in the physical and biogeochemical state of the Southern Ocean are already 187 underway. The circumpolar Southern Ocean is warming more rapidly, and to greater 188 depth, than the rest of the global ocean (Gille, 2002; 2008). The upper layers of the 189 Southern Ocean have freshened as the result of increases in precipitation and the 190 melting of floating glacial ice (Curry et al. 2003; Boyer et al., 2005; Böning et al., 191 2008). Freshening of Antarctic Bottom Water (AABW) in the Indian and Pacific 192 regions of the Southern Ocean may also reflect an increase in basal melting of floating 193 glacial ice (Jacobs, 2004; 2006; Aoki et al., 2005; Rintoul, 2007), with increased 194 melt linked to increased heat flux from the ocean (Shepherd et al, 2004; Rignot et al., 195 2008). Widespread warming of AABW has been observed (Zenk and Morozov, 2007; 196 Johnson and Doney, 2006); this is believed to be due to a combination of changes in 197 formation properties, and changes in export processes driven by climate variability 198 (Meredith et al., 2008). 199 200 Since 1992, the satellite altimeter record shows an overall increase in sea level and 201 strong regional trends linked to shifts in fronts of the ACC (Sokolov and Rintoul, 202 2009a,b). The average circumpolar extent of sea ice shows a small but significant 203 increase during the satellite era (post-1978) (Comiso and Nishio, 2008), due primarily 204 to large increases in the Ross Sea sector that are nearly compensated by large 205 decreases west of the Antarctic Peninsula (where rates of decrease rival those seen in 206 the Arctic; Stammerjohn et al., 2008). The regional trends in sea ice extent have been 207 linked to changing meridional winds associated with the strengthening trend of the 208 Southern Annular Mode (Turner et al., 2009). While some coupled models suggest 209 that the overall extent could increase as melt water increases stratification and 210 insulates the surface layer from warmer deeper water (Zhang, 2007), the IPCC 4AR 211 models suggest sea ice is likely to decline by about 30% by 2100 (Bracegirdle et al., 212 2008). Turner et al. (2009b) suggest that the recent increase in Antarctic sea ice 213 extent is linked to the depletion of stratospheric ozone and that significant declines in 214 sea ice are likely in the future as ozone levels recover and the impact of increasing 215 greenhouse gases is more strongly felt. Models also suggest that sea ice thickness will 216 decline more rapidly than ice extent, but there are no observations with which to 217 assess whether sea ice thickness has changed. 218 219 The uptake of CO2 by the ocean is changing the ocean’s chemical balance by 220 increasing the total inorganic carbon concentration, increasing the acidity and altering 221


6

the carbon speciation (Vazquez-Rodriguez et al., 2009). Because of the temperature 222 dependence of the saturation state of calcium carbonate, the cold waters in the polar 223 regions will be the first to cross the aragonite under-saturation threshold (Orr et al., 224 2005; McNeil and Matear, 2008). There is some evidence that the changes are already 225 causing a reduction in calcification of the shells of some organisms (Moy et al., 226 2009). A common planktonic response to increased CO2 is an increase in primary 227 productivity under higher CO2 (e.g. Tortell et al., 2008) with changes to the 228 elementary stoichiometry (e.g. Bellerby et al., 2008). Subsequent changes in the 229 quantity and nutritional quality of primary production will have consequences for 230 secondary production, food web carbon and energy flows and biogeochemical 231 cycling. The response of the Southern Ocean food web to changes in ocean chemistry 232 remain largely unknown. 233 234 The Southern Ocean harbours unique and distinct ecosystems as a result of its 235 isolation and extreme environment (e.g. Laws, 1985). Phytoplankton biomass is 236 generally low, despite high concentrations of macronutrients, often ascribed to the 237 lack of the micronutrient iron (Holm–Hansen et al. 2004a,b; Korb & Whitehouse 238 2004; Korb et al. 2005; Blain et al. 2007). The Southern Ocean food web is 239 characterized by a keystone species, Antarctic krill (Euphausia suberba), which 240 supports large populations of higher predators (Murphy et al 2007). This relative 241 dependence on a single species and the uniqueness of the Southern Ocean food webs 242 and biogeochemical cycles make the system vulnerable to climate variability and 243 change. There is evidence of changes in other components of the Southern Ocean 244 food web, from phytoplankton to penguins and seals (Fraser et al., 1992; Loeb et al., 245 1997; Reid and Croxall, 2001; Fraser and Hofmann 2003; Weimerskirch et al., 2003; 246 Murphy et al., 2007; McClintock et al., 2008). However, most biological and 247 ecological time series are short, incomplete and limited to a particular location, 248 making it difficult to assess and interpret long-term trends. Often the physical and 249 chemical measurements needed to link ecosystem variability to environmental 250 variability do not exist. Possible synergistic interactions between harvesting of 251 Southern Ocean resources and climate change are largely unknown and may alter 252 assessments of the sustainability of these activities. 253 254

1.3TheneedforasustainedSouthernOceanObservingSystem255

256 The recent advances summarised above underscore the importance of the Southern 257 Ocean in the Earth system. Improved understanding of the links between Southern 258 Ocean processes, global climate, biogeochemical cycles and marine productivity will 259 be critical for society to respond effectively to the challenges of climate change, sea-260 level rise, ocean acidification and the sustainable use of marine resources. In 261 particular, it is critical to understand how the Southern Ocean system will respond to 262 changes in climate and other natural and human forcing and the potential for 263 feedbacks. To achieve this enhanced understanding, sustained multi-disciplinary 264 observations are essential. 265 266 Research programmes over the past 15 years have demonstrated that sustained 267 observations of the Southern Ocean are feasible. For example, repeat hydrographic 268 sections have been used to quantify the evolving ocean inventory of heat and carbon, 269 to demonstrate that changes are occurring throughout the full depth of the Southern 270


7

Ocean, and to provide a platform for a wide suite of interdisciplinary observations. 271 Satellites are providing circumpolar, year-round coverage of physical and biological 272 variables and sea ice properties. Moorings are providing time series information on 273 velocities and water properties in critical regions. The development of autonomous 274 profiling floats (Argo) now allows broad-scale, year-round measurements of the 275 interior of the Southern Ocean (to 2 km depth) to be made for the first time. The 276 ocean beneath the sea ice, inaccessible with traditional platforms, is being measured 277 with special polar profiling floats and miniaturised oceanographic sensors attached to 278 marine mammals. Ocean gliders now offer the possibility of making real-time 279 multidisciplinary measurements of the upper 1000 m of the water column, and have 280 recently been deployed for the first time in the Antarctic. Measurements of biological 281 distributions and processes using net tows, continuous plankton recorders, and 282 acoustics are providing new insights into the coupling of physical, biogeochemical 283 and ecological processes. Autonomous underwater vehicles are providing new insight 284 into the ocean deep beneath ice shelves. 285 286 These developments are a striking success, and go far beyond what could have been 287 envisioned just a decade ago (Rintoul et al., 2002). In particular, the emphasis then 288 was on maintaining the traditional hydrographic, high-density Expendable 289 Bathythermographs (XBTs), and mooring arrays, and a call for Argo, with its focus 290 on the upper ocean heat budget, to include the Southern Ocean. The fruits of this 291 effort can now be seen in terms of upper ocean salinity observations by Argo and 292 marine mammals that reveal an enhanced freshwater cycle (e.g. Durack and Wijffels, 293 2010), with important changes occurring in the Southern Ocean. 294 295 While existing tools allow the backbone of the SOOS to be established, new 296 technologies are needed in some areas before the observing system is complete. This 297 is particularly true for biogeochemistry and biology, where there are as yet no 298 platforms to provide broad-scale measurements of key variables in a cost-effective 299 manner. Efforts are underway to develop sensors that extend the capability of Argo 300 floats, animal platforms, gliders, moorings and ships of opportunity and these 301 developments will be particularly important in the poorly observed Southern Ocean. 302 The increase in tourism and fisheries in the Southern Ocean opens up new 303 possibilities for observations to be collected as part of the Voluntary Observing Ship 304 Programme (VOS). The SOOS will be a test bed for these instruments and provide the 305 complementary data sets needed for their interpretation. 306 307 The capability to model and simulate Southern Ocean processes has also improved 308 dramatically in recent years. Increasingly, models are an integral element of ocean 309 observing systems. Models are needed to interpolate between sparse observations, to 310 integrate diverse observations into consistent estimates of the state of the ocean, to 311 detect the significance of variations in time scales beyond the duration of 312 observations, to infer aspects of the ocean circulation that are not directly observable 313 (e.g. vertical velocity), to integrate circulation and biological observations and to 314 conduct quantitative observing system design studies. In atmospheric science, the 315 wide availability of high quality atmospheric reanalyses has led to dramatic advances 316 in understanding. Ocean science is at the beginning of a similar revolution, with the 317 first global state estimates only recently produced. It is likely that in the future ocean 318 scientists, like their atmospheric counterparts, will rely heavily on ocean analyses 319 produced by combining data and dynamics rather than on the results of individual 320


8

observations, cruises or experiments. These ocean state estimates, in turn, depend on 321 access to sustained, broad-scale observations. 322 323

1.4AVisionforaSouthernOceanObservingSystem324

325 An integrated observing system for the Southern Ocean has been advocated for at 326 least a decade (e.g. Rintoul et al., 1999; Summerhayes, 2004, 2007; Sarukhanian and 327 Frolov, 2004; Summerhayes et al., 2007). This was explored at a workshop in Hobart 328 in 2006, instigated by the Partnership for Observations of the Global Ocean (POGO), 329 the Census for Antarctic Marine Life (CAML), SCAR and SCOR. At the meeting 330 and in subsequent discussions with the broader community there has been strong 331 support for a SOOS. Three further meetings organised by SCAR and SCOR with the 332 support of CAML, the Global Ocean Observing System (GOOS), the World Climate 333 Research Programme (WCRP), POGO and NOAA have been held. As input to these 334 meetings, a survey was conducted of researchers and research users to identify the top 335 priorities for the SOOS. The SCAR/SCOR Expert Group on Oceanography and the 336 CLIVAR/CliC/SCAR Southern Ocean Region Implementation Panel have taken the 337 lead in producing the SOOS strategy, though views have been solicited from as wide 338 a range of interested parties as possible. 339 340 The community involved in developing the SOOS concept reached broad consensus 341 that a Southern Ocean Observing System must be: 342

• sustained, 343 • feasible and cost-effective, 344 • circumpolar, extending from the Subtropical Front to the Antarctic 345

continent and from the sea surface to the sea floor, 346 • multi-disciplinary (including physics, biogeochemistry, sea ice, biology, 347

and surface meteorology), 348 • targeted to address specific scientific challenges, 349 • integrated with the global ocean and climate observing systems, 350 • based initially on proven technology but evolving as technology develops, 351 • integrated with a data management system built on existing structures, 352 • able to deliver observations and products to a wide range of end-users, and 353 • built on past, current and future research programmes. 354

355

1.5Purposeandstructureofthestrategy356

The purpose of this Initial Science and Implementation Strategy is to highlight the 357 scientific relevance of the Southern Ocean, articulate the need for sustained 358 observations to address major outstanding scientific challenges, and to provide a road-359 map for implementation of the SOOS. Chapter 2 outlines the scientific rationale for 360 sustained observations of the Southern Ocean. Chapter 3 identifies six key 361 challenges for Southern Ocean science, summarises the sustained observations needed 362 to meet them and outlines a draft strategy to obtain the observations. A summary of 363 the current status of Southern Ocean observations and an initial roadmap for 364 implementation of the SOOS is presented in Chapter 4. 365 366 367 368


9

2. Rationale for a Southern Ocean Observing System 369

2.1RoleoftheSouthernOceaninclimateandglobalbiogeochemicalcycles370

371 The Southern Ocean overturning circulation consists primarily of two counter-rotating 372 cells (Figure 1). Deep water formed in the North Atlantic spreads south to the 373 Southern Ocean and is carried east by the ACC. This water spreads poleward (in 374 some cases after first passing through the deep Indian and Pacific basins) and shoals 375 across the ACC, reaching the surface over a range of latitudes and densities. Water 376 upwelling close to Antarctica is converted first by freshening and subsequently by 377 cooling and addition of brine released by sea ice formation to denser AABW, which 378 sinks from the continental shelf to the deep ocean. Slightly less dense deep water 379 upwells at lower latitude, beneath the westerly winds where surface waters are driven 380 north in the Ekman layer. Gain of heat and freshwater in the surface layer converts 381 the upwelled deep water to less dense water that subducts as Antarctic Intermediate 382 Water and Subantarctic Mode Water. The strength of this upper cell of the 383 overturning circulation is controlled by eddy fluxes and air-sea forcing (Figure 2). 384 385

386 Figure 1: A representation of the global overturning circulation, from Lumpkin and 387 Speer (2007). The Southern Ocean connects the ocean basins, through the Antarctic 388 Circumpolar Current, and connects the upper and lower limbs of the global 389 overturning circulation, through water mass transformation. 390 391


10

392 Figure 2: A sketch of the ACC system showing the zonal flow and the meridional 393 overturning circulation and watermasses. Antarctica is at the left side. The east-west 394 section displays the isopycnal and sea surface tilts in relation to submarine ridges, 395 which are necessary to support the bottom form stress that balances the wind. The 396 curly arrows at the surface indicate the buoyancy flux, the arrows attached to the 397 isopycnals represent turbulent mixing. From Olbers et al. (2004), redrawn from a 398 figure from Speer et al. (2000). 399 400 401 The overturning circulation largely determines the overall exchange rate between the 402 surface layers and the ocean interior, and therefore how much heat and carbon the 403 ocean can store. Much of the increase in heat stored by the ocean is found in the 404 Southern Ocean, where the overturning circulation has transferred heat from the 405 surface to the ocean interior (Figure 3). 406 407

408 409 Figure 3: Linear trend (1955–2003) of the zonally integrated heat content of the 410 world ocean by one-degree latitude belts for 100-m thick layers. Heat content values 411 are plotted at the midpoint of each 100-m layer. Contour interval is 2 x 1018 J year-1. 412 Levitus et al. (2005). 413


11

414 The overturning circulation also influences the global cycle of carbon and nutrients. 415 Subduction of intermediate water and mode water in the upper cell of the Southern 416 Ocean sequesters CO2 in the ocean interior, so the Southern Ocean as a whole is a 417 significant sink of carbon: the ocean south of 30°S accounts for about 40% of the total 418 oceanic inventory of anthropogenic CO2 (Figure 4). Upwelling of carbon-rich deep 419 water at high latitudes results in outgassing of carbon dioxide to the atmosphere and 420 wind-driven variations in the Southern Ocean overturning therefore drive changes in 421 ocean uptake of CO2 (Le Quéré et al., 2007; Lovenduski et al., 2007; Lenton and 422 Matear, 2007; Verdy et al., 2007; Butler et al., 2007). 423 424

425 426 Figure 4: Column inventory of anthropogenic CO2 in the ocean. High inventories are 427 associated with Deep Water formation in the North Atlantic and Intermediate and 428 Mode Water formation between 30°-50°S. Total inventory of shaded regions is 429 106±17 Pg C. Sabine et al. (2004). 430 431 432 The upwelling of deep water in the Southern Ocean returns nutrients to the surface 433 ocean at high latitudes. A fraction of the upwelled nutrients is not utilized in the 434 Southern Ocean and is exported to lower latitudes in mode and intermediate waters. 435 The nutrient input supports biological productivity not just in the Southern Ocean but 436 worldwide: model studies suggest that nutrients exported from the Southern Ocean 437 by the upper cell of the overturning support 75% of oceanic primary production north 438 of 30°S (Sarmiento et al. 2004). 439 440 However, while evidence for the critical role played by the Southern Ocean in global 441 budgets of heat, freshwater, carbon and nutrients continues to accumulate, many 442 uncertainties remain. Eddy fluxes make a significant contribution to meridional 443 exchange of mass and heat across the Southern Ocean and vertical exchange of 444 momentum (Rintoul et al., 2001), but the extent to which eddy fluxes and Ekman 445 transport compensate each other in the mixed layer is unresolved. Coarse resolution 446 climate models that include parameterisations of eddy processes, rather than resolving 447 them directly, suggest that an increase in winds over the Southern Ocean would result 448 in an increase in the strength of the overturning circulation. However, models that 449


12

resolve eddies suggest that the equatorward Ekman transport and poleward eddy 450 transport tend to compensate one another, resulting in a reduced change in the 451 strength of the overturning circulation (e.g. Hallberg and Gnanadesikan, 2006). 452 Resolving this issue is critical to understanding how changes in forcing may affect the 453 Southern Ocean overturning and the capacity of the ocean to store heat and carbon. 454 Ocean observations have been interpreted as evidence that the real ocean is closer to 455 the latter case (Böning et al., 2008), but this result requires testing with sustained 456 observations and better understanding of the underlying dynamics. 457 458 The possibility that increased freshwater input to the high latitude ocean could cause a 459 slowing of the thermohaline circulation, driving an abrupt change in climate, has 460 attracted considerable interest (Alley et al., 2003). Most attention has focused on the 461 North Atlantic, where a significant decrease in the salinity of North Atlantic Deep 462 Water (NADW) has been observed during the past four decades (e.g. Dickson et al., 463 2002). (The reversal of this long-term freshening trend in recent years demonstrates 464 the significant influence of decadal variability.) However, the Southern Ocean also 465 makes an important contribution to the global overturning, by connecting the shallow 466 and deep limbs of the overturning circulation and by forming dense waters that make 467 a similar contribution to ventilation of the deep ocean to that made by NADW (e.g. 468 Orsi et al., 2002). Evidence for freshening of the Southern Ocean continues to grow, 469 with freshening observed in the upper ocean (Boyer et al., 2005; Böning et al., 2008), 470 in the Ross Sea (Jacobs et al., 2002; Jacobs and Giulivi, 2010), and in Antarctic 471 Bottom Water (Aoki et al., 2005; Jacobs, 2004, 2006; Rintoul, 2007). Sustained 472 observations of the freshwater budget are needed to assess the likelihood of future 473 changes in the overturning circulation. Model studies further suggest that 474 perturbations of the freshwater and heat balance at high southern latitudes can have 475 rapid and widespread influence on climate and ocean properties, by generating waves 476 that rapidly transmit this climate signal on hemispheric or global scales (e.g. Ivchenko 477 et al., 2004; Richardson et al., 2005; Masuda et al., 2010). 478 479 The ACC is the primary means of exchange of mass, heat and freshwater between the 480 ocean basins. Recent advances in observations, models and theory have provided new 481 insights into the dynamics and structure of the current, the role of eddies and 482 topographic interactions, and the dynamical connections between the ACC and the 483 overturning circulation (Rintoul et al., 2001; Olbers et al., 2004; Sokolov and Rintoul, 484 2007). The sensitivity of the ACC transport to changes in forcing remains a topic of 485 debate. Coarse resolution models, such as those used in the IPCC assessments, tend 486 to suggest that the ACC transport is more sensitive to changes in wind forcing (Fyfe 487 2006, Fyfe et al., 2007), while models that explicitly resolve eddies show a weaker 488 response (e.g. Hallberg and Gnanadesikan, 2006; Meredith and Hogg, 2006). Long-489 term observations of ACC transport indicate only a moderate response of ACC 490 transport to changes in the winds (Meredith et al., 2004), whilst observations of the 491 density structure of the ACC also indicate relatively little change in recent decades 492 (Böning et al., 2008). Sustained observations of ACC transport are needed to resolve 493 this question and to quantify basin-scale budgets of heat, freshwater and other 494 properties. 495

2.2Seaiceandiceshelves496

497


13

Antarctic sea ice influences climate and affects the interaction between the ocean and 498 atmosphere in a number of important and complex ways. During winter, the 499 Antarctic sea ice covers approximately 19 x 106 km2, a larger area than the continent 500 itself, and decreases to 20% of this amount during summer (Figure 5). The ice 501 surface can reflect up to 90% of the incident solar radiation, depending on its 502 thickness and snow cover, while the ice-free open ocean absorbs a similar fraction. 503 Even a relatively thin cover of first year ice with a few centimetres of snow 504 significantly increases the surface albedo of the ocean. A decrease in sea ice extent, 505 on the other hand, reduces the albedo and warms the ocean, providing a positive 506 feedback that drives further melt. The salt released when sea ice forms is also key in 507 dense water production. 508 509 Coastal polynyas, where strong katabatic winds drive the ice offshore as rapidly as it 510 forms, are regions of intense air-sea interaction and water mass formation. When sea 511 ice melts, the additional freshwater increases the stability of the surface layer and 512 affects air-sea exchange, water mass formation and the depth of the mixed layer. The 513 formation and melting of sea ice therefore influences the light and nutrient 514 environment experienced by phytoplankton in the sea ice zone. Sea ice also strongly 515 influences air-sea exchange of heat, moisture and gases. The presence of a 10 cm 516 thick layer of sea ice reduces air-sea heat loss by 90%. Changes in sea ice extent have 517 been linked to large swings in atmospheric CO2 between glacial and interglacial 518 periods. 519 520 Sea ice is also closely related to biological productivity in the marine ecosystem. It 521 provides a habitat for some species and a platform for others. Microorganisms are 522 trapped in the sea ice structure as it forms, often in higher concentrations than occur in 523 the water column, and then released again when the sea ice melts. During their time 524 within the ice environment, some species thrive while the growth of others is either 525 inhibited or stopped completely. Gradients of temperature and salinity within the ice 526 dictate the living conditions for organisms trapped there while the thickness of snow 527 cover determines the amount of light available. High concentrations of algae are 528 often observed near the bottom of the ice, providing food for krill. Krill is a key 529 component of the food chain and a primary source of food for baleen whales, seals, 530 penguins and other birds. Changes in sea ice extent would therefore be expected to 531 have impacts on the entire Antarctic food chain. For example, declines in sea ice 532 extent have been linked to a reduction in krill biomass and an increase in salps, at 533 least in some regions of Antarctica (Figure 5, Atkinson et al., 2004), and to changes at 534 higher trophic levels (Barbraud et al. 2000) 535 536


14

537 538 Figure 5: Temporal change of krill and salps. a, Krill density in the SW Atlantic 539 sector (4,948 stations in years with .50 stations). Temporal trends include b, post-540 1976 krill data from scientific trawls; c, 1926–2003 circumpolar salp data south of 541 the southern boundary of the Antarctic Circumpolar Current. 542 543 Sea ice extent and concentration can be measured from a variety of satellite 544 instruments (e.g. Figure 6), and algorithms continue to be improved (e.g. Lubin and 545 Massom, 2006). Sea ice thickness (and volume) is of greater importance for many 546 climate questions (e.g. the high latitude freshwater balance) but is much more 547 challenging to observe. In the Arctic, long time series of ice thickness measurements 548 from upward-looking sonars on submarines have revealed a 1.3 m decrease in mean 549 ice draft in the central Arctic basin (Thorndike et al., 1999) between 1958-76 and 550 1993-97. The changing ice thickness distribution for the same period has been 551 reported by Yu et al. (2004) and shows substantial losses occurred in ice thicker than 552 2 m and a significant increase in ice 1-2 m thick. Thickness measurements in the 553 Antarctic are limited to sparse ship observations that have been compiled into a 554 climatology for the period 1980 - 2005 (Worby et al., 2008) and even more sparse 555 measurements from moored instruments (Strass and Fahrbach, 1998; Worby et al., 556 2001) and in situ drilling (e.g., Wadhams et al., 1987). 557 558


15

100%

98%

94%

90%

86%

82%

78%

74%

70%

66%

62%

58%

54%

50%

46%

42%

38%

34%

30%

26%

22%

18%

14%

10%

<8%

a) F ebruary, 2003

b) Oc tober, 2003

559 560 Figure 6: Minimum (February) and maximum (October) sea ice extent around 561 Antarctica for 2003 from AMSR-E passive microwave data. Courtesy J. Comiso, 562 NASA/Goddard Space Flight Centre, USA. 563 564 565 Melt of glacial ice, in the form of icebergs or floating ice shelves and glacier tongues, 566 also makes an important contribution to the high latitude freshwater balance. Interest 567 in the basal melt of floating ice has increased with growing evidence that the 568 continental ice sheets can respond rapidly to changes in the floating ice that acts as a 569 “buttress” to inhibit the flow of ice to the sea. For example, the rapid collapse of the 570 Larsen-B ice shelf was followed by a dramatic acceleration of the flow of glaciers 571 feeding the ice shelf (Rignot et al., 2004; Pritchard and Vaughan, 2007). If the ice 572 sheets respond rapidly to changes in the floating ice, present estimates of the rate of 573 future sea level rise may be too conservative (IPCC 4AR). In the Antarctic, warmer 574 ocean temperatures have been linked to an increase in the basal melt rate and the 575


16

retreat of grounding lines in Antarctica (Figure 7, Rignot, 2008): a 1°C increase in 576 ocean temperatures increases basal melt rates by ~10 m yr-1 (Rignot and Jacobs, 577 2002). The dynamic response of the ice sheets will be determined largely by what 578 happens in the ocean, as air temperatures over the Antarctic continent are unlikely to 579 increase enough to cause widespread surface melting, unlike Greenland. Reducing 580 the uncertainty in future estimates of sea level rise requires observations of changes in 581 ocean temperature and circulation and an improved understanding of ocean-ice shelf 582 interaction. Ice shelves are just beginning to be added to climate models, but the ice 583 balance depends strongly on oceanic properties and circulation not well represented in 584 the present state of modelling; hence long-term observations of the ocean near and 585 beneath ice shelves are crucial for model verification and improvement. 586 587

588 589 590

Figure 7: Ice velocity of Antarctica colour coded on a logarithmic scale and overlaid 591 on a MODIS mosaic13. Circles denote mass loss (red) or gain (blue) of large basins 592 in gigatonnes per year. Drainage basins are black lines extending from the grounding 593 -line flux gates. From Rignot et al., 2008. 594

2.3SouthernOceanbiologyandecology595

596 The Southern Ocean includes some of the most productive and unique marine 597 ecosystems on Earth (Figure 8). These marine ecosystems were heavily exploited in 598 the past. Sustainable management of marine resources requires the ability to 599 distinguish the effects of human exploitation (e.g. harvesting) from the effects of 600


17

climate variability and change (see discussions in Ainley et al., 2005; Nicol et al. 601 2008). For the Southern Ocean, distinguishing these effects is difficult because of 602 limited observations and understanding of how changes in the physical environment 603 are linked to changes in ecosystem structure or function. 604 605

606 607 608 Figure 8: A generalised Southern Ocean food web from the level of krill upwards. 609 Four main size groups of animals (each in a coloured ellipse) are shown. Each 610 animal is shown to scale within each ellipse. Scale bars are present in each ellipse 611 along with a measurement in metres showing how big the bar would be in its natural 612 size. Squid and lantern fish are used for comparing scales between ellipses. Lower 613 orange ellipse: (1) Antarctic krill, (2) lantern fish. Lower middle red ellipse: (2) 614 lantern fish at new scale, (3) Adélie penguin, (4) mackerel icefish, (5) squid. Upper 615 middle green ellipse: (5) squid at new scale, (6) crabeater seal*, (7) white-chinned 616 petrel*, (8) Antarctic fur seal, (9) Patagonian toothfish, (10) leopard seal*, (11) 617 southern elephant seal*. Top blue ellipse: (5) squid at new scale, (12) orca* (13) 618 sperm whale*, (14) minke whale*, (15) humpback whale*, (16) southern right 619 whale*, (17) blue whale*. (Source: * indicates illustrations by Brett Jarrett from 620 Shirihai, 200757; Adélie penguin photo – A. Cawthorn; Other photos – A. Constable). 621 From Constable and Doust (2009). 622 623 The Southern Ocean ecosystems are structured broadly by latitude, or rather by the 624 quasi-zonal structure of the ACC (e.g. Treguer and Jacques, 1992; Grant et al., 2006; 625 Figure 9) and by depth. In the silica-limited waters north of the Sub-Antarctic Front, 626


18

dinoflagellates, small flagellates, coccolithophores and small zooplankton dominate 627 the plankton community. Diatoms become increasingly dominant to the south in the 628 “high nutrient, low chlorophyll (HNLC)” waters of the ACC, where primary 629 production is believed to be limited by lack of iron. The presence of high productivity 630 areas in the wake of island sources of iron, such as South Georgia, Crozet and 631 Kerguelen, supports this notion. The seasonal sea ice zone is by far the most 632 productive region of the Southern Ocean. In particular, it is the main foraging region 633 for a large number of air-breathing predators (seals, whales, penguins and other 634 birds). The main prey is krill, whose life cycle is strongly associated with sea ice. 635 636

637 638 639 Figure 9: Bioregionalisation of the Southern Ocean. Grant et al. (2006) 640 641 An observed decline in krill in the southwest Atlantic has been linked to a reduction 642 in sea ice (Atkinson et al., 2004) and is likely to result in a shift in the community 643 structure and associated food webs as they move from krill dominated to non-krill 644


19

dominated (Figure 10)(Murphy et al. 2007). In the Western Antarctic Peninsula, ice-645 dependent Antarctic species (Adélie penguin Pygoscelis adeliae and Weddell seal, 646 Leptonychotes weddellii) are being replaced by open water sub-Antarctic species 647 (Gentoo, P. papua and Chinstrap, P. antarctica penguins, and southern fur, 648 Arctocephalus gazella and elephant, Mirounga leonina, seals) (e.g. Fraser et al. 1992, 649 Fraser & Patterson 1997, Ducklow et al. 2007). 650 651

652 Figure 10: from Murphy et al. (2007, Figure 5). 653 654 The Southern Ocean ecosystem is generally assumed to be controlled by the supply of 655 nutrients and light that are needed for photosynthesis by primary producers. This 656 bottom-up control suggests that the ecosystem will be sensitive to changes in physical 657 forcing that influence the light and nutrient environment experienced by 658 phytoplankton (e.g. upwelling, mixed layer depth, sea ice). Phytoplankton are integral 659 to determining biogeochemical fluxes and the export of carbon and nutrients from the 660 surface ocean to the deep sea. The efficiency of the biological pump depends on a 661 range of environmental and biological factors, which are in turn affected by climate 662 change. Simultaneous measurements of the physical and chemical forcing, 663 environmental structure, and the biological and ecological responses are required to 664 develop the mechanistic understanding that is required to predict the response of 665 ecosystems and carbon export to climate change. In addition, predators exert controls 666 on ecosystem structure and function (top-down control), which contribute to 667 ecosystem variability (Ainley et al., 2005). Top predators are important for preserving 668 ecosystem structure and function (Rooney et al., 2006), transferring energy between 669 the interacting species of the trophic system. To differentiate between bottom-up and 670 top-down controls, integrated observations of physics and biology across multiple 671 trophic levels are required. 672 673


20

Understanding the response of marine biota to climate forcing is important both for 674 climate and for management of marine resources. Phytoplankton mediate the 675 biogeochemical fluxes of carbon, oxygen and nitrate by transferring carbon and 676 nutrients from the surface ocean to the deep sea. The efficiency of the biological 677 pump depends on a number of factors, each of which is potentially influenced by 678 climate forcing. For example, the fraction of primary production that is exported 679 depends on the species and size class of the phytoplankton and zooplankton 680 communities, which in turn can be influenced by changes in the mixed layer depth 681 and the supply of macro- and micro-nutrients, including iron. 682 683 The biological pump also influences the Antarctic benthos, which is rich in biomass 684 on the shelves and rich in species in the deep-sea. However, it is still not known to 685 what degree benthic assemblages reflect temporal processes in the water column or 686 are relatively uncoupled from primary productivity, being an adaptive heritage from 687 past climate cycles. These processes determine the final fate of organic carbon in the 688 ocean. The nearshore benthos is influenced strongly by sea ice processes and scour by 689 icebergs can cause local disturbances (Stark et al., 2005; Smith et al., 2006). Some 690 Antarctic benthic organisms are physiologically adapted to these natural changes, but 691 others have limited ability to adapt to variations in the environment, such as warming 692 (Peck et al., 2006). Conservation and management of marine ecosystems requires that 693 the impact of human activities, such as fishing and waste disposal near research 694 stations, can be distinguished from the impact of climate variability and change. 695 Long-term observations of the forcing and response of the system are needed to 696 provide the knowledge of system behaviour needed to inform managers and decision-697 makers. 698 699 Past research programs have provided knowledge of particular aspects of Southern 700 Ocean ecosystems, such as controls on primary production, the biology and ecology 701 of Antarctic krill, copepod life cycles, and predator foraging and behaviour. More 702 recent research programs like the Global Ocean Ecosystem Dynamics (GLOBEC) 703 programme and the Palmer LTER have attempted to integrate ecological and 704 environmental measurements to provide a more complete view of particular 705 ecosystems, for example the physical and biological factors that contribute to the 706 survival and success of krill populations throughout the year (Hofmann et al. 2004, 707 2008; Schofield et al., 2010). However, we still lack the mechanistic understanding 708 and modelling tools to predict the ecosystem response to climate variability and 709 change. A critical gap is the lack of sustained, integrated observations that span 710 disciplines and a range of time and space scales. 711

2.4ObservedChangesintheSouthernOcean712

713 Southern Ocean processes influence climate change and variability, biogeochemical 714 cycles, sea-level rise and marine productivity, as described above. Changes in the 715 Southern Ocean would therefore have significant implications. In this section, we 716 summarize some of the evidence for change in the Southern Ocean and consider 717 projections of future change. A more complete overview of changes in Antarctica and 718 the Southern Ocean is provided by Mayewski et al. (2009), Turner et al. (2009a), 719 Convey et al (2009), and Schofield et al. (2010). 720

Large-scale changes 721


21

722 The most pronounced change in the Southern Ocean is the circumpolar warming of 723 the Southern Ocean in the region of the ACC in recent decades (Figure 11) (Gille 724 2002; Gille 2008; Levitus et al. 2005), the rate of which exceeds that of the global 725 ocean as a whole. While the warming is surface-intensified, with magnitudes of more 726 than a tenth of a degree C per decade near the surface, the signal extends to more than 727 1000 m depth. As a result of this deep-reaching temperature change, more heat has 728 been stored in the Southern Ocean as the Earth warms than in any other latitude band. 729 730

731 732

Figure 11: Profiles of temperature difference between 1990s temperature profiles 733 and hydrographic data sorted by decade. Differences are computed as 1990s 734 reference temperatures minus historic temperature profiles sorted by decade, using 735 the nearest neighbour method discussed in the text. Here results are presented for 736 summer data (November through March), averaged first by latitude band. [Gille, 737 2008]. 738 739 Other physical and chemical properties of the Southern Ocean are also changing 740 (Bindoff et al., 2007). Salinity has decreased in the water masses exported from the 741 Southern Ocean in the upper limb of the overturning circulation (Wong et al., 1999; 742 Curry et al., 2003; Aoki et al., 2005a; Durack and Wijffels, 2010). Antarctic Bottom 743 Water (AABW) has become fresher and less dense in the Indian and Pacific sectors 744 since the late 1960s (Jacobs 2004, 2006; Aoki et al., 2005b; Rintoul, 2007). The 745 freshening of AABW reflects at least in part the strong freshening on the Ross Sea 746 shelf, where salinity has reduced by more than 0.2 since 1950, a decline linked to an 747 increase in glacial melt in the southeast Pacific sector (Jacobs et al., 2002; Jacobs and 748 Giulivi, 2010; Figure 12). Oxygen concentrations have reduced below the base of the 749


22

mixed layer, south of the ACC (Aoki et al., 2005a). Long time series from the 750 Weddell Sea do not show a similar trend, and act as a reminder that decadal 751 variability can complicate the interpretation of short and incomplete records. 752 753

754 Figure 12: Freshening of Ross Sea shelf waters between 1960 and 2008. [Jacobs 755 and Giulivi (2010).] 756 757 Many of the large-scale and regional changes in the physics and chemistry of the 758 Southern Ocean have been linked to changes in wind forcing, in particular the 759 intensification and southward contraction of the circumpolar westerly winds 760 associated with a positive trend of the Southern Annular Mode (SAM, (Thompson et 761 al. 2000). Mechanisms linking stronger winds to circumpolar ocean warming include 762 a southward shift in the location of the ACC, increased heat flux into the ocean, and 763 increased mesoscale eddy activity (Fyfe 2006; Fyfe et al. 2007; Gille 2008; Hogg et 764 al. 2008; Meredith and Hogg 2006). The trend in the SAM has been attributed to 765 human activities, including greenhouse gas emission and ozone depletion (e.g. 766 Marshall 2003; Thompson and Solomon 2002; Fyfe et al., 2007). The overall 767 warming of the surface ocean, increase in precipitation and ice melt, and changes in 768 sea ice extent and thickness have also likely contributed to the observed changes. To 769 make further progress in understanding how climate change and variability are 770 driving change in the Southern Ocean, sustained observations of the ocean 771 stratification and circulation are needed. 772 773 There is fragmentary evidence of changes in the Southern Ocean ecosystem. The 774 range of the coccolithophorid Emiliania huxleyii has now extended south into the sea-775


23

ice zone within the last decade, possibly in response to global warming (Cubillos et al. 776 2007; Mohana et al. 2008). Changes in seabird and krill abundance have been noted 777 in particular areas (e.g. Croxall et al. 2002, Atkinson et al. 2004). It is well 778 established that the effect of environmental variability propagates throughout the 779 marine food web with significant impacts (Croxall 1992, Waluda et al. 1999, Forcada 780 et al. 2005, Barbraud and Weimerskirch 2001; Barbraud and Weimerskirch 2006, 781 Jenouvrier et al. 2003; Jenouvrier et al. 2005; Jenouvrier et al. 2006; Weimerskirch et 782 al. 2003) Leaper et al. 2006, , Clarke et al. 2007, Barnes & Peck 2008, Murphy et al. 783 2007, Trathan et al. 2007a) and for some systems these changes can be profound and 784 long lasting (e.g. Costa et al. 1989). A number of impressive biological time series 785 exist, such as the Emperor penguin time series at Dumont d’Urville that starts in 1952 786 (Figure 13, Barbraud and Weimerskirch 2001) and on the western Antarctic peninsula 787 (Figure 14, McClintock, 2008). However, there are usually few observations of 788 change in the physical environment near these colonies, thus we are not currently able 789 to relate changes in predator populations to changes in environmental forcing. A 790 SOOS would provide the oceanographic context needed to better understand the 791 environmental factors responsible for such demographic changes. 792 793

794 Figure 13. From Barbraud and Weimerskirch (2001). 795


24

796 797 Figure 14: Changes in the number of breeding pairs in penguin rookeries near 798 Palmer station, western Antarctic Peninsula. As the amount of sea ice declines, ice-799 dependent Adélie penguins are declining and being replaced by sub-polar Gentoo 800 penguins. McClintock et al. (2008). 801 802

Sea Ice Variability 803

804 In contrast to the Arctic, where large decreases in sea ice extent and thickness have 805 occurred, trends in the circumpolar extent of Antarctic sea ice are weak but generally 806 positive (Stammerjohn and Smith, 1997; Watkins and Simmonds, 2000; Yuan and 807 Martinson, 2000; Zwally et al., 2002; Parkinson, 2004; Comiso and Nishio, 2008). 808 Regional changes in sea ice extent and the seasonality of advance and retreat have 809 been recorded in the Pacific sector (Figure 15, Stammerjohn et al., 2008), with 810 substantial impacts on the marine ecosystem (Wilson et al., 2001). Direct 811 observations of sea ice extent are limited to the satellite era. Proxies for sea ice extent 812 based on historical whaling (de la Mare, 1997) and ice core records (Curran et al., 813 2003) suggest a decline in sea ice extent occurred between the 1950s and 1970s, but 814 these results remain somewhat controversial (e.g. Ackley et al., 2003). While 815


25

information on changes in sea ice extent in Antarctica are limited, even less is known 816 about changes in sea ice thickness (and therefore volume). In this regard, it is notable 817 that climate models suggest that Arctic sea ice thickness will change more rapidly 818 than extent, with total volume projected to decrease at approximately double the rate 819 of ice thickness (Gregory et al., 2002). 820 821

822 Figure 15: The 1979–2004 trend (days/year) in ice season duration. The black/white 823 contours delimit the 0.01/0.10 significance levels. Within the sea ice zone, gray 824 shading signifies near zero trend. [Stammerjohn et al., 2008] 825 826

Carbon Dioxide Uptake and Ocean Acidity 827

828 Carbon uptake by the Southern Ocean has acted to reduce atmospheric CO2 829 concentrations and thereby to slow the rate of climate change. As a result of the 830 increased burden of CO2, the surface waters of the Southern Ocean have become more 831 acidic and surface pH has decreased by around 0.1. Ocean acidification is expected to 832 affect a wide range of calcifying organisms, with the impacts felt first in the cold 833 waters of the Southern Ocean due to the temperature dependence of aragonite 834 solubility (Orr et al 2005, Royal Society Report 2005, Hunt et al. 2008, McClintock et 835 al., 2009; Fabry et al., 2009). However, the response to ocean acidification is poorly 836 understood, varies with species, and the response of the ecosystem as a whole almost 837 entirely unknown. 838 839


26

Studies based on inversion of atmospheric carbon dioxide data (Le Quéré et al. 2007) 840 and coarse resolution ocean models (Lovenduski et al., 2007, 2008; Zickfeld et al., 841 2007; Verdy et al., 2007; Lenton and Matear, 2007) conclude that the positive trend in 842 the SAM has caused a reduction in the ability of the Southern Ocean to absorb CO2. 843 In these studies, the poleward shift and intensification of the westerly winds drives 844 enhanced equatorward Ekman transport and therefore enhanced upwelling of deep 845 water rich in dissolved inorganic carbon (DIC) (e.g. Hall and Visbeck, 2002). The 846 increased supply of deep water causes more outgassing of natural carbon dioxide from 847 the deep ocean, decreasing the effectiveness of the Southern Ocean sink of CO2. 848 Warmer surface waters will also dissolve less atmospheric CO2 than will colder 849 waters. The link between increases in the wind field, isopycnal tilt and upwelling in 850 the presence of eddies is not direct, as discussed previously, however changes in DIC 851 and 14C in high latitude surface waters are consistent with an increase in upwelling 852 (Metzl et al., 2009). The issue is presently a topic of vigorous debate. Resolving the 853 issue is critical to assess the sensitivity of the Southern Ocean carbon sink to climate 854 change and the potential for feedbacks. Observations of the evolving ocean inventory 855 of carbon are needed, as well as further model studies. 856 857

Regional Variability 858

859 Rapid change has been observed in particular regions of the Southern Ocean. The 860 most notable example of this is the western side of the Antarctic Peninsula, where the 861 atmosphere has warmed more rapidly than anywhere else in the southern hemisphere 862 in recent decades. Here, a wintertime warming in excess of 5ºC over 50 years has 863 been observed (King et al. 2004; Vaughan et al. 2003), with a smaller rate of warming 864 seen in summer. These atmospheric changes are strongly associated with a marked 865 retreat of sea ice extent, warming of the upper ocean and more rapid melt of ice 866 shelves (Meredith and King 2005). 867 868 Changes in sea ice and ocean properties at the western Antarctica Peninsula have had 869 profound ecological consequences. According to Ducklow et al. (2007), “the western 870 Antarctic Peninsula is experiencing the most rapid warming of any marine ecosystem 871 on the planet.” Marine species in this region are typically well adapted to cope with 872 low temperatures, but poorly adapted to cope with changes in temperature. Population 873 and species level losses of some marine organisms can be expected at the western 874 Peninsula in response to a change in ocean temperature of 2ºC (Peck et al. 2004). The 875 observed warming is over half this amount already, in just a few decades, raising the 876 possibility of serious disruption to the marine ecosystem here in the near future. 877 Indeed, some significant shifts in different trophic levels have already been observed 878 in response to the warming (e.g. Ducklow, 2008, McClintock, 2008, and related 879 papers). The region is also a key breeding and nursery ground for Antarctic krill, an 880 important species in the Southern Ocean food web. Atkinson et al. (2004) suggest 881 krill numbers in this region have strongly declined as a result of ocean warming and 882 loss of sea ice. The rapid pace of environmental change, a long record of 883 interdisciplinary observations, and relatively easy logistics make the western 884 Antarctic Peninsula an excellent laboratory for studying the effects of climate change 885 and variability on ecosystem function. 886 887


27

888 889 Figure 16 Upper left: surface atmospheric temperature change at Faraday and 890 Rothera stations on the western Antarctic Peninsula. Temperature change here has 891 been the most rapid in the southern hemisphere, with most of the warming 892 concentrated in the winter months. Upper right: coupled to the atmospheric warming 893 (and retreat of sea ice), a strong warming of the upper ocean has occurred in recent 894 decades, which acts as a positive feedback on the climate change, and which has 895 profound implications for the local and regional ecosystems (Meredith and King, 896 2005). Lower: the climate change at the Peninsula has also profoundly affected the 897 glacial ice field, with the majority of marine-terminating glaciers in retreat, and with 898 retreat rates accelerating in recent years (Cook et al., 2005). 899 900 Projections of future change 901 902 Predicting future change in the Southern Ocean is particularly challenging. Small-903 scale phenomena like ocean eddies, which are unresolved by climate models, play a 904 particularly important role in the Southern Ocean. Observations are scarce for testing 905 of ocean models and for developing improved parameterisations. Existing models 906 often do not perform well in the Southern Ocean. For example, an ocean carbon 907 model intercomparison study found that the models diverged most dramatically in the 908 Southern Ocean, primarily because of differences in how the models simulated the 909 stratification and circulation (Orr et al., 2005). 910 911 Faced with a set of divergent IPCC AR4 model projections, one approach is to form a 912 “weighted average” of a number of models in which higher weight is placed on results 913 from models that do a better job of simulating high latitude climate (Bracegirdle et al., 914


28

2008). The weighted mean model results predict further warming of the air over the 915 Southern Ocean over the next century (Figure 17a), a 25% reduction in sea ice 916 production, and a continued increase in strength of the westerly winds. 917 918 Averaging 19 IPCC AR4 model outputs for sea surface temperatures similarly 919 provides a reasonable estimate of future change (Fig 17b, from Wang and Meredith, 920 2008, reproduced in Turner et al 2009a). The SST changes are smaller than those 921 observed in surface air temperature (Fig 17a) because the heat capacity of the ocean is 922 much larger than that of the atmosphere. Both the air temperatures and the ocean 923 temperatures will affect the sea ice. Close to the coast warming is likely to reach 0.5° 924 to 1.0°C, perhaps rising to 1.25°C in the Amundsen Sea, in summer (Fig 17b). Winter 925 temperatures are likely to be much as they are today, perhaps up to 0.5°C warmer. 926 Bottom water temperatures are likely to change in much the same way over the 927 continental shelf (Turner et al., 2009a). 928 929 It is likely that warming and freshening of the surface layer will increase the 930 stratification of the upper ocean, reducing nutrient inputs to the euphotic zone. 931 Biological productivity and ecosystem function are also likely to be affected by a 932 reduction in sea ice (cf McClintock et al., 2008). With regard to acidification in the 933 Southern Ocean, whilst there is considerable uncertainty surrounding its speed of 934 progression, climate models using a business-as-usual scenario for CO2 emissions 935 (IS92a) predict that the surface waters will become undersaturated with respect to 936 aragonite by 2050, extending through the entire Southern Ocean by 2100 (Orr et al., 937 2005). As noted by McNeil and Matear (2008), when the seasonality of the carbonate 938 ion concentration is taken into account, the saturation threshold is crossed several 939 decades earlier. 940 941

942

Figure 17a. Predicted trends in surface temperatures over the next 100 years from a 943

weighted average of the IPCC AR4 coupled models. Note the widespread warming of 944

the air over the Southern Ocean, which is strongest in the Weddell and Ross Seas 945


29

owing to the retreat of the sea ice there and the consequent change in albedo. From 946

Bracegirdle et al. (2008). 947

948

949 950 Figure 17b. Sea surface temperature change between 2000 and 2100 in summer (a) 951 and winter (b). From Wang and Meredith (2008) and Turner et al., 2009a). 952 953


30

2.5InformingDecision‐makers954

955 In addition to climate effects, human pressures on the Southern Ocean are increasing 956 and will likely continue to do so. Further exploitation of marine resources is likely as 957 more traditional sources of protein decline or increase in cost. Antarctic tourism is a 958 rapidly growing industry and the effects of this industry on the environment requires 959 monitoring and regulation (e.g. Enzenbacher, 1992; Fraser and Patterson, 1997; 960 Frenot et al., 2005). Increased use of the Southern Ocean will increase the need for an 961 effective search and rescue capability, guided by the best available information on 962 ocean conditions. As the number of vessels using the Southern Ocean increases, the 963 risk of an oil spill or other contaminant release also increases, further underscoring the 964 need for timely and accurate information on ocean currents. Geo-engineering 965 solutions (e.g. iron fertilisation of the Southern Ocean; see Watson et al. (2008) and 966 accompanying articles) are being considered as mitigation strategies for CO2 removal. 967 Increased use of the Southern Ocean will result in greater demand for knowledge to 968 manage resources and to inform decisions by policy makers, industry and the 969 community. 970 971 972

3. Design of a Southern Ocean Observing System 973

3.1Keysciencechallengesandtheneedforsustainedobservations974

975 Based on the rationale above, six overarching Southern Ocean science challenges can 976 be identified, each of which requires sustained observations to be addressed. 977

1. The role of the Southern Ocean in the global heat and freshwater balance 978 979 Changes in the polar water cycle will have global impacts due to the sensitivity of the 980 overturning circulation and heat transport to changes in freshwater input (Broecker, 981 1997, Clark et al., 2002). Observations suggest changes in the global water cycle may 982 already be apparent in changes in ocean stratification (e.g. Durack and Wijffels, 983 2010). The stratification of the Southern Ocean is delicately poised and particularly 984 sensitive to changes in the freshwater balance (Gordon, 1991). Substantial 985 uncertainty remains with regard to the high-latitude contributions to the global water 986 cycle, the sensitivity of the water cycle to climate change and variability, and the 987 impact of changes in the high latitude water cycle on the rest of the globe. 988 989 Freshwater fluxes from melting sea ice, sub-ice shelf melting and precipitation are of 990 the same order of magnitude in the Southern Ocean (Hellmer and Timmerman, 2004), 991 and all three components need to be measured. Variables that need to be measured 992 include atmospheric circulation (winds, storms, evaporation, precipitation, moisture 993 flux); the horizontal and vertical circulation of the ocean, including exchange between 994 high and low latitudes and the circulation beneath the sea ice, through the annual 995 cycle; sea ice extent, thickness and distribution; and the contribution of glacial ice (ice 996 shelf melt and iceberg production). New satellites promise synoptic observations of 997 aspects of the freshwater balance, including snow and ice thickness, that can not be 998


31

measured at high spatial or temporal resolution using conventional means, but these 999 new sensors are in critical need of data sets for validation. 1000

2. The stability of the Southern Ocean overturning circulation 1001 Climate models suggest the overturning circulation in both hemispheres is sensitive to 1002 climate change (e.g. IPCC, 2007). Enhanced greenhouse warming is expected to 1003 drive a more vigorous hydrological cycle, with increased precipitation at high 1004 latitudes and increased evaporation at low latitudes. The resulting reduction in 1005 surface salinity reduces the formation of dense water at high northern and southern 1006 latitudes. Paleoclimate records demonstrate that changes in the overturning circulation 1007 have been associated with large and abrupt climate changes in the past (e.g. Clark et 1008 al., 2002). Changes in strength of the Southern Ocean overturning circulation have 1009 been linked to changes in the ocean uptake and release of carbon dioxide, both in the 1010 present day ocean and in association with glacial – interglacial cycles. Sustained 1011 observations of temperature, salinity, stratification and ventilation are needed to detect 1012 changes in the overturning in response to changes in atmospheric forcing. The 1013 observations need to span the entire water column and include carbon, oxygen and 1014 other tracers. 1015

3. The role of the ocean in the stability of the Antarctic ice sheet and its future 1016 contribution to sea-level rise 1017 The largest uncertainty in assessments of future sea-level rise concerns the polar ice 1018 sheets (IPCC, 2007). Recent evidence that the dynamic response of ice sheets to 1019 changes in forcing can be much more rapid than previously believed has added 1020 urgency to this issue. For most of Antarctica (i.e. outside of the Antarctic Peninsula), 1021 air temperatures are projected to remain below the freezing point of ice for centuries. 1022 Basal melting of ice by warm ocean waters will therefore play a primary role in 1023 determining the future behaviour of ice sheets and glaciers buttressed by floating ice 1024 shelves (Rignot, 2008). Sustained observations of ocean temperatures near the ice 1025 shelves are needed to assess basal melt rates, and salinity and stable isotope 1026 measurements are needed to detect the input of meltwater and its impact on ocean 1027 stratification. 1028

4. The future and consequences of Southern Ocean carbon uptake 1029 Climate models suggest the Southern Ocean uptake of carbon dioxide will decrease as 1030 a result of changes in circulation and stratification caused by enhanced greenhouse 1031 warming, providing another potential positive feedback for climate change (Sarmiento 1032 et al., 1998). As discussed above, recent studies have highlighted the sensitivity of 1033 the global carbon cycle to changes in the Southern Ocean. The uptake of carbon by 1034 the ocean results in acidification and changes in carbonate chemistry that will likely 1035 have significant but largely unknown consequences for life in the ocean. Full water 1036 column sections of carbon, oxygen, nutrients and physical variables are needed to 1037 track the evolving inventory of anthropogenic CO2 and other properties related to the 1038 carbon and biogeochemical cycles. Additional surface observations are needed to 1039 complement the water column measurements to improve the spatial coverage. 1040

5. The future of Antarctic sea ice 1041 Sea ice influences climate through its contribution to the freshwater balance, water 1042 mass formation, albedo, and modulation of air-sea exchange of heat and gases. Sea 1043 ice also provides important habitat for Antarctic organisms including algae, krill, 1044


32

penguins and seals, and influences productivity in the ocean by supplying iron and 1045 meltwater to influence mixed layer depth and the light environment. While there has 1046 been little change in the total extent of Antarctic sea ice in recent decades, there have 1047 been strong regional trends in ice extent and duration, and models predict a decline in 1048 sea ice extent and volume in the future. A sustained observing system for Antarctic 1049 sea ice will rely heavily on remote sensing from satellites and aircraft, but these 1050 methods are critically dependent on in situ observations for validation and algorithm 1051 development. 1052

6. Impacts of global change on Southern Ocean ecosystems 1053 A better understanding of the impact of global change on Southern Ocean ecosystems 1054 (Clarke et al 2007, Barnes & Peck 2008) is essential to guide conservation and marine 1055 resource management decisions. Our ability to predict changes in marine resources 1056 and biodiversity, to assess ecosystem resilience, and determine feedbacks between 1057 food webs and biogeochemical cycling depends on sustained, integrated observations 1058 of key physical, chemical and biological parameters. High priority variables to 1059 measure include: primary production, distribution and abundance of key species 1060 and/or functional groups, benthic community structure, top predator abundance, 1061 distribution (both geographical and in relation to physical structure) and diet. 1062 Simultaneous measurements of the physical and chemical environment are needed, 1063 including pH, temperature, salinity, mixed layer depth, wind speed and direction, 1064 meteorological conditions, sea ice conditions, currents, and nutrients. Studies of 1065 predator species can reveal “hot spots” of foraging activity (or Areas of Ecological 1066 Significance (AES)) and changes in foraging and demographic parameters that reflect 1067 changes in lower trophic levels (e.g. zooplankton, fish and squid) that are difficult to 1068 observe directly. 1069 1070

3.2BuildingblocksofanintegratedSouthernOceanObservingSystem1071

1072 Having defined the key overarching science challenges, variables that needed to be 1073 observed on a sustained basis were identified (Table 1). For each variable, multiple 1074 platforms or techniques could be used to deliver the sustained observations (Table 2). 1075 Each of the challenges requires a different mix of observations, but there is substantial 1076 overlap as well. For example, each of the themes depends on sustained observations 1077 of the stratification of the upper ocean (i.e. temperature and salinity as a function of 1078 space and time). A number of platforms and techniques can be used to measure the 1079 upper ocean stratification, including Argo floats, repeat hydrographic sections, 1080 underway measurements, animal-borne sensors, gliders, and ice-tethered platforms. 1081 Similarly, improved understanding of the response of marine ecosystems to 1082 environmental change requires sustained observations of a wide range of physical, 1083 chemical and biological variables. In the following, we discuss each of the “building 1084 blocks” of an integrated observing system in turn, including how the measurement 1085 contributes to SOOS, what sampling is needed, present status and gaps, and 1086 recommendations. 1087

1088


33

1088 Table 1: A summary of the variables for which sustained measurements are required 1089 to address the key scientific challenges. The entries in the list of variables are short-1090 hand for a number of related variables (e.g. “carbon” refers to pCO2, DIC, POC, 1091 PIC, alkalinity). 1092

1093 1094

Key science challenges

Fre

shw

ater

b

alan

ce

Ove

rtu

rnin

g

circ

ula

tio

n

Ice

shee

t st

abili

ty

and

sea

-lev

el r

ise

Fu

ture

of

sea

ice

Car

bo

n a

nd

b

iog

eoch

emis

try

Imp

act

on

ec

osy

stem

s

stratification (T(z),S(z))

velocity tracers carbon pH nutrients oxygen sea ice wind air-sea flux (heat, FW)

sea surface height

seabed pressure

particulates phytoplankton zooplankton benthos fish birds

Var

iab

les

req

uir

ed t

o b

e m

easu

red

mammals 1095


34

Table 2: The combination of platforms and techniques needed to provide sustained 1095 observations of each of the fields identified in Table 1. 1096 1097

Platforms and techniques

rep

eat

hyd

rog

rap

hy

Arg

o

un

der

way

sam

plin

g

mo

ori

ng

s

anim

al s

enso

rs

sig

hti

ng

su

rvey

s &

cam

eras

CP

R

glid

er/A

UV

RO

V &

imag

ing

met

ho

ds

sate

llite

ice

stat

ion

s

aco

ust

ics

traw

ls/n

ets

bo

tto

m la

nd

ers/

core

rs

dri

fter

s

stratification (T(z),S(z))

SST, SSS velocity tracers

CO2 nutrients

ph oxygen

DMS aerosols

wind air-sea flux (heat,

FW)

sea surface height seabed pressure

particulates phytopl’ton zooplankton

fish birds

mammals predators benthos

1098 1099 Access to historical data 1100 Given the lack of observations from the Southern Ocean, it is particularly critical that 1101 historical data are accessible and their quality assessed. Significant efforts have been 1102 made to do this for physical oceanographic data and to a lesser extent with sea ice, 1103 chemical and biological data sets. However, much data still resides with the 1104 originating investigators, are in formats and media that are not easily accessible, 1105 require standardisation to reduce biases, or may have large uncertainties that need to 1106 be quantified. Upper trophic level and hydroacoustic data sets are examples of the 1107 latter. The compilation of zooplankton net tow data sets (KRILLBASE, Atkinson et 1108 al. 2009) provides an example of the value of compiling historical biological data sets 1109 in a consistent manner and making the resulting data base easily accessible. 1110 1111 Recommendations: The biogeochemical and ecological data sets (e.g. animal 1112 tracking) need to be integrated with historical environmental data (e.g. hydrographic 1113 climatologies). Many of these data sets are available via a range of data management 1114


35

systems. A common data portal is needed to provide access to multi-disciplinary data 1115 sets (e.g. SCAR-MarBIN which provides comprehensive biodiversity data). The 1116 SOOS needs to ensure that both past and future data sets are accessible and 1117 comparable. 1118 1119 Repeat hydrography 1120 Repeat hydrographic sections provide the backbone of a multidisciplinary SOOS. 1121 Repeat hydrography provides water samples for analysis of properties for which in 1122 situ sensors do not exist, the highest precision measurements for analysis of change 1123 and for calibration of other sensors, accurate baroclinic transport estimates, a platform 1124 for a wide range of ancillary measurements and the only means of sampling the full 1125 ocean depth. CLIVAR (the CLimate VARiability and Predictability project of the 1126 World Climate Research Programme) and the global carbon survey have re-occupied 1127 many of the sections occupied during the World Ocean Circulation Experiment 1128 (WOCE). During the International Polar Year (IPY), a near-synoptic circumpolar 1129 snapshot of the Southern Ocean was obtained. 1130 1131 Recommendations: Figure 18 shows the WOCE/CLIVAR repeat hydrographic lines to 1132 be repeated as part of SOOS. This plan is consistent with the programme of global 1133 repeat hydrographic sections (Hood et al., 2010). To document the changing 1134 inventory of heat, freshwater and carbon dioxide, the sections need to be repeated on a 1135 5 to 7 year time-scale. Annual occupations of the Drake Passage line are needed. The 1136 transects should include measurements of physical (e.g. CTD (Conductivity-1137 Temperature-Depth), O2, Shipboard and Lowered Acoustic Doppler Current Profilers 1138 (SADCP/LADCP), tracers, oxygen-18, biogeochemistry (e.g. nutrients, trace elements 1139 and micronutrients, carbon, isotopic measurements of export flux, dimethyl sulphide 1140 (DMS)), and biology (e.g. primary production, pigments, bio-optics, fast repetition 1141 rate fluorometer, molecular diversity, biomarkers, targeted trawls, net tows, acoustic). 1142 The sections should extend from north of the ACC to the Antarctic coast, including 1143 the sea ice zone and the continental slope and shelf (therefore the high latitude 1144 sections need to be sampled using ice-capable vessels). The programme of CTD 1145 sections across the Antarctic slope and shelf by research and supply vessels travelling 1146 to and from Antarctic bases initiated by the SASSI (Synoptic Antarctic Shelf Slope 1147 Interactions) project for IPY should be continued and placed on a more operational 1148 basis (Figure 19). 1149 1150

1151 1152 1153 1154


36

1155 Figure 18: Repeat hydrographic sections to be occupied by SOOS. Symbols indicate 1156 the WOCE/CLIVAR designations for each line. 1157 1158 1159

1160 1161 1162 Figure 19: Hydrographic sections (lines) and moorings (circles) occupied as 1163 contributions to the IPY SASSI program. Many of these lines are near Antarctic 1164 bases and could be repeated more regularly as a contribution to the SOOS. 1165 1166


37

Enhanced Southern Ocean Argo 1167 All of the key science challenges require sustained, broad-scale measurements of the 1168 ocean state, measurements that can only be obtained using autonomous platforms 1169 such as profiling floats. A sustained commitment to maintenance of a profiling float 1170 array in the Southern Ocean is critical. Argo has made a particularly significant 1171 contribution to observations of remote areas like the Southern Ocean; already there 1172 are more profiles collected from Argo floats than from the entire history of ship-based 1173 oceanography in this region. As an example, Figure 20 shows the location of profiles 1174 collected south of 30°S during the 24 month IPY period. Floats with oxygen sensors 1175 are beginning to be deployed in the Southern Ocean; we can anticipate that with time 1176 the capacity to measure additional variables from floats will increase. The float array 1177 needs to extend to seasonally ice-covered seas, through the use of ice-capable floats 1178 and acoustic tracking of floats. 1179 1180 Recommendations: The first priority is to maintain the Argo network at the nominal 1181 Argo density (1 float per 3 degree longitude x 3 degree latitude square, or roughly 970 1182 floats south of 40°S). As seen in Figure 21, there is still some way to go to reach this 1183 level of coverage. The extension of the system to sample under sea ice is also 1184 important, as some of the most important changes are occurring near the ice shelves 1185 and within the sea ice zone. Floats capable of deeper profiling would be of particular 1186 value in the Southern Ocean, where significant changes have been observed below 1187 2000 m. Oxygen sensors will provide useful information on ventilation processes and 1188 the carbon cycle. Sensors to measure a wider range of biological and chemical 1189 parameters (e.g. bio-optics) are needed to relate variations in the physical 1190 environment to biogeochemistry and ecosystem processes. 1191 1192

1193 1194 Figure 20: The location of more than 60,000 Argo profiles of temperature and 1195 salinity collected during the 24 months of the IPY. Courtesy of Mathieu Balbeoch, 1196 JCOMMOPS. 1197 1198


38

1199 1200 Figure 21: The status of the Argo array in the Southern Ocean, as of May 2010. 1201 Despite the progress in recent years, large regions of the high latitude Southern 1202 Ocean remain poorly observed. Courtesy of Mathieu Balbeoch, JCOMMOPS. 1203 1204 Underway sampling from ships 1205 The full hydrographic sections need to be complemented by more frequent underway 1206 sampling transects, to reduce aliasing of signals with time-scales shorter than the 5-7 1207 year repeat cycle of the repeat hydrography (the issue of seasonal aliasing remains, as 1208 most underway measurements are made between October and March). While 1209 underway measurements are generally limited to the surface layer, use of ships of 1210 opportunity provide a cost-effective means of collecting a wide range of physical, 1211 biogeochemical and biological observations: temperature, salinity, velocity (from 1212 ADCP), pCO2, pH, nutrients, fast repetition rate fluorometry (FRRF), plankton (from 1213 CPR), phytoplankton pigments, surface meteorology and Expendable 1214 Bathythermographs and CTDs (XBTs/XCTDs) to provide measurements of upper 1215 ocean thermal structure along the ship track, including mixed layer depth (the 1216 Japanese Antarctic Research Expeditionis (JARE), the French Ocean Indien Service 1217 d'Observation (OISO), and Australia-France Astrolabe programs provide an example 1218 of what is required). However, few ships at present measure this complete suite of 1219 variables. Aerosol sampling from ships is needed to quantify the aeolian input of iron 1220 and other trace elements to the Southern Ocean. 1221 1222 Recommendations: The present underway sampling system is shown in Figure 22. 1223 There is a need to maintain and expand the fleet of ships making routine 1224 measurements of the Southern Ocean and to increase the number of variables 1225 measured on each line. Antarctic resupply ships and tourist vessels remain 1226 underexploited. Autonomous sampling devices (e.g. Ferry Box) should be installed 1227 on additional vessels. Upgrading the surface meteorology measurements made on 1228 these vessels is a high priority and will help improve the poorly constrained air-sea 1229 flux estimates over the Southern Ocean. A comprehensive review of requirements for 1230 monitoring changes to the global ocean-atmosphere carbon flux can be found in 1231 Schuster et al (XXX). 1232


39

1233 1234 Figure 22: The ship-of-opportunity lines in the Southern Ocean that contribute to 1235 SOOS. 1236 1237 Acidification detection system: As the ocean absorbs CO2 and becomes more 1238 acidic, the saturation threshold for aragonite will be crossed first in the cold waters of 1239 the polar regions. Sustained observations of both ocean chemistry and the effect of 1240 changing ocean chemistry on organisms are required. Feely et al. (2010) outline the 1241 requirements for sustained observations to track ocean acidification and its impacts. 1242 The repeat hydrography, underway observations, and Argo floats armed with 1243 chemical sensors discussed above will provide the primary means of measuring DIC, 1244 alkalinity, pCO2 and pH. Time series measurements from moored sensors should be 1245 deployed in key regions. 1246 1247 Recommendations: Establish network and protocols for sampling of calcareous 1248 plankton and benthic organisms, to detect effects of changes in acidification and 1249 saturation state of the Southern Ocean. This will need to be complemented by 1250 simultaneous measurements of pCO2, alkalinity and pH to determine the saturation 1251 state of calcite and aragonite and the depth of the saturation horizon. For critical 1252 regions such as the high latitudes and coastal areas, abundances and distributions of 1253 key taxa should be tracked with sufficient precision and resolution to detect possible 1254 shifts corresponding to observed changes in the geochemical parameters. There is an 1255 immediate need for baseline data on calcifying organisms in regions that are projected 1256 to become undersaturated with respect to aragonite in the coming decades, such as the 1257 Southern Ocean. Rapid, cost-effective technologies for quantifying abundances of 1258 targeted organisms should be a central component of any integrated ocean 1259 acidification observation network. 1260 1261 Continuous monitoring of key passages and locations 1262 Several key passages and boundary currents in the Southern Ocean are high priorities 1263 for sustained observations because of their role in the global-scale ocean circulation 1264 (Figure 23). The presence of energetic variability at a range of periods means that 1265


40

continuous observations from moored arrays are needed in passages and boundary 1266 currents to provide year-round sampling and to help de-alias infrequent repeat 1267 hydrography. Tide gauges and bottom pressure recorders have been shown to provide 1268 a cost effective means of monitoring the variability in the transport of the ACC on 1269 timescales from weeks and months (Hughes et al., 2003) to years (Meredith et al., 1270 2004). At longer timescales, tide gauge data from the Antarctic coast and Southern 1271 Ocean islands form a critical part of the global sea-level observing system. 1272 1273 Recommendations: High priority regions for sustained moored measurements include 1274 Drake Passage, along the prime meridian (eg the Weddell Sea Convection Control 1275 (WECCON) and Goodhope programs south of Africa) and the locations of deep 1276 outflows (e.g. the western Weddell Sea and the deep boundary current on the eastern 1277 flank of the Kerguelen Plateau, the Princess Elizabeth trough, and the Ross Sea and 1278 Adélie Land bottom water outflows). The existing array of tide gauges and bottom 1279 pressure sensors needs to be maintained and extended to the western hemisphere. The 1280 Antarctic Slope Front and Antarctic Coastal Current make a significant contribution 1281 to inter-basin exchange and therefore need to be measured on a sustained basis. 1282 Likewise, the Agulhas and Tasmanian limbs of the southern hemisphere “supergyre” 1283 (Speich et al., 2002) provide important inter-basin connections with consequences for 1284 climate and therefore need to be monitored. 1285

1286

1287 1288 Figure 23: Map of proposed moored arrays (red circles) to sample the primary 1289 Antarctic Bottom Water formation and export sites, as part of a coordinated global 1290 array to measure the deep limb of the global overturning circulation. Each of these 1291 sites has been occupied in recent years. The map shows the inventory of 1292 chlorofluorocarbon 11 (CFC-11) in the density layer corresponding to AABW (from 1293 Orsi et al., 1999). 1294 1295 1296


41

Animal-borne sensors 1297 Oceanographic sensors deployed on birds and mammals can make a significant 1298 contribution to a SOOS in two ways: by relating predator movements and behaviour 1299 to fine-scale ocean structure (Biuw et al. 2007; Burns et al. 2004), and by providing 1300 profiles of temperature and salinity from regions of the Southern Ocean that are 1301 difficult to sample by other means (e.g. beneath the winter sea ice; Charrassin et al. 1302 2008, Figure 24; Costa et al. 2008; Nichols et al., 2008). The animals also often 1303 provide high resolution transects across the Southern ocean frontal zones (e.g. 1304 Boehme et al., 2008). Because the tags can also monitor changes in body condition of 1305 the animals (e.g. Biuw et al. 2007), they can provide a link to changes in the animal’s 1306 resource acquisition and impacts of observed and modelled oceanographic change on 1307 populations of top predators. 1308 1309 Recommendations: Maintain the network of seal tag deployments established during 1310 IPY (Figure 25), to provide information on seal foraging behaviour and its 1311 relationship to environmental variability and on the in situ oceanographic conditions 1312 in the open ocean and in the sea ice zone in winter (see Boehme et al., 2008, Nicholls 1313 et al., 2008). (See also the section on “Ecological monitoring via top predators” 1314 below.) 1315 1316 Table 3. Summary of the possible species, age/sex classes and locations for CTD 1317 SLDR deployments as part of SOOS. These have been chosen to provide optimal 1318 spatial and temporal coverage, guided by experience during the IPY and earlier 1319 tagging programs. 1320 1321

Weddell Seals Southern Elephant seals Adult females Adult females Sub-adult males

Winter Habitat

Inshore fast ice

No. of tags

Possible countries

Winter Ice Edge/ Frontal zones

No. of tags

Possible countries

Antarctic continental shelf

No. of tags

Possible countries

East Antarctica (Davis)

7 Australia Macquarie Island

10 Australia Macquarie Island

10 Australia

East Antarctic (DDU)

7 France Isles Kerguelen

10 France Isles Kerguelen

10 France

WAP 10 USA/UK Marion Island

10 South Africa

Marion Island

10 South Africa

Weddell Sea (Drescher Inlet)

10 Germany/UK South Georgia

10 UK Bovetoya 10 Norway

Ross Sea 10 USA/New Zealand

Elephant Island

10 Brazil WAP 10 USA/UK

Location/Region

South Georgia

10 UK

1322 1323 1324


42

1325 1326 Figure 24. Temperature field at 500 m during 2004–2005 from the Coriolis database 1327 and from the merged Coriolis and elephant seal databases. Mean front positions 1328 during the same period derived from Coriolis (A) or Coriolis and seal temperature 1329 field at 500m(B) (thick lines), and from altimetry (thin lines in A and B). Plotted 1330 fronts are the southern boundary of the ACC (Bdy)], southern branch of the southern 1331 ACC front , and central branches of the Polar Front (PF) and the Subantarctic Front 1332 (SAF). Note the increased level of detail in the combined plots. (From Charrassin et 1333 al. 2008; front names follow Orsi et al., 1999 and Sokolov and Rintoul, 2007). 1334 1335 1336

1337 1338 1339 Figure 25. Surface temperature and location of 67,904 CTD profiles collected by 1340 seals during the Marine Mammals Exploring the Oceans Pole to Pole (MEOP) 1341 program during IPY. 1342 1343 1344 Sea ice observations 1345 Measurements of both the extent (period, seasonality) and thickness (volume) of sea 1346 ice are needed to understand the role of Antarctica in the climate system. A variety of 1347 satellite instruments provide continuous, circumpolar observations of sea ice extent, 1348 with varying spatial resolution. Measuring sea ice volume, however, remains a 1349 significant challenge. Recent advances in radar and laser altimetry may be the key to 1350 providing information on sea ice thickness, however Antarctic sea ice poses a number 1351 of challenges that have yet to be overcome. In particular, most Antarctic sea ice is 1352


43

relatively thin and therefore has a relatively small freeboard measurement, making 1353 altimetry methods more difficult. The widespread formation of snow ice through 1354 surface flooding and refreezing also complicates altimetry measurements. 1355 1356 Recommendations: A variety of tools will be needed to meet the challenge of 1357 providing sustained measurements of sea ice thickness and extent: AUVs and fixed-1358 point moorings with ice-profiling sonars, acoustically-tracked floats with ice thickness 1359 sonars, ship-board observations including ice drift stations, remote sensing and data-1360 assimilating models. The most critical observations to make are those that can be 1361 used to validate remote sensing measurements, as satellites provide the only means to 1362 sample sea ice over broad areas. A circumpolar “snapshot” of Antarctic sea ice 1363 thickness fields should be obtained as soon as possible to provide a baseline against 1364 which future change can be assessed. Regional-scale ice and snow thickness data 1365 should be obtained using a range of techniques including AUVs which measure ice 1366 draft from an upward looking sonar, and airborne techniques such as laser and radar 1367 altimetry and electromagnetic induction. Ideally “ice-edge to coast” transects in 1368 different seasons, and targeting regions with varying conditions, would provide the 1369 necessary information on regional and temporal changes in conditions as assessed by 1370 the Antarctic Sea Ice Processes and Climate (ASPeCt) programme (Figure 26, Worby 1371 et al., 2008). In situ measurements of ice and snow thickness properties, particularly 1372 density, are also essential for interpreting these data. The AUV programme will also 1373 collect oceanographic and biological data as well as ice thickness (e.g. salinity, 1374 temperature, currents, sonar for biology). Time series of ice thickness from fixed-1375 point moorings are needed to complement the spatial sampling from the AUV 1376 programme as well as more systematic collection of Antarctic sea ice thickness 1377 measurements, including ASPeCt observations and IceCam, from additional research, 1378 supply and tourist vessels. Recovery of historical Antarctic sea ice thickness data 1379 from individual investigators is essential for establishing a longer baseline of 1380 observations and a data portal has been established at the Australian Antarctic Data 1381 Centre for this purpose and for archiving all other data on Antarctic sea ice properties 1382 ((http://data.aad.gov.au/aadc/seaice ). 1383

1384 1385 Figure 26: Annual mean sea ice thickness derived from ASPeCt ship observations 1386 (Worby et al., 2008). Units are metres. 1387


44

1388 Surface drifters: Additional surface drifters are required to provide better coverage 1389 of sea-level pressure (SLP) and sea surface temperature (SST) for input to numerical 1390 weather prediction (NWP) models, and hence improve the quality of the air-sea fluxes 1391 provided by the models; to provide SST measurements for removal of biases in 1392 satellite products; and to measure velocity and temperature in the ocean mixed layer 1393 and so provide insight into the surface ocean heat budget (e.g. Moisan and Niiler, 1394 1998) and circulation (e.g. Niiler and Maximenko, 2003). 1395 1396 Recommendations: Maintain surface drifter sampling in the Southern Ocean to at 1397 least the density of the global requirement of 1250 drifters worldwide or at least 2-3 1398 drifters per 10 degree box (Zhang et al., 2006) (Figure 27). 1399 1400

1401

1402 Figure 27: Status of the global surface drifter array in May 2010 (top) and the 1403 equivalent buoy density (EBD) for January – March 2010 produced by NOAA. 1404 Yellow and red squares indicate regions where observations from ships and drifters 1405 fall below the required density. Note the lack of drifter data close to the Antarctic 1406 coast (but see Figure 28) 1407 1408


45

Enhanced sea ice drifter array 1409 Our understanding of the intense and highly variable ocean-ice-atmosphere 1410 interactions taking place in the Antarctic sea ice zone is poor due to the lack of 1411 observations. Numerical weather predictions south of 60°S suffer from a lack of 1412 surface pressure observations from the Sea Ice Zone (SIZ); as a consequence, flux 1413 products derived from reanalyses of the numerical weather prediction (NWP) models 1414 are also uncertain. An example of the coverage of drifters deployed by the 1415 International Program for Antarctic Buoys is shown in Figure 28. At present, few ice 1416 drifters are being deployed. 1417 1418 Recommendations: The target is for circum-Antarctic buoys spaced every 500 to 1419 1000 km in the zonal and meridional directions, consistent with the typical correlation 1420 length scale of variations in sea-level pressure and air temperature. A smaller number 1421 of “mass balance buoys” is needed to measure ice and snow thickness, providing 1422 crucial ground-truth for new satellite sensors. Dense clusters of buoys need to be 1423 deployed in some locations for detailed studies of ice dynamics and deformation. 1424 Further work is required to define these requirements. 1425 1426

1427 1428 Figure 28: The complete record of Ice drifter trajectories from the International 1429 Program for Antarctic Bouys (IPAB), compiled over a number of years. The 1430 relatively dense sampling in the Weddell Sea and off East Antarctica indicates the 1431 efforts of the German and Australian sea ice programs in recent decades. The buoy 1432 drifts illustrate the circulation of the subpolar gyres and the overall divergent drift to 1433 the north, indicating that repeated seeding of floats is required to maintain coverage. 1434 1435 1436 1437


46

Ocean circulation under sea ice 1438 With few exceptions (e.g. Nichols et al., 2008) the ocean circulation and structure 1439 beneath the Antarctic sea ice remains largely unknown. New technologies now allow 1440 ocean currents and stratification beneath the sea ice to be observed for the first time. 1441 The strategy for sub-ice observations in the Antarctic will rely heavily on technology 1442 being developed for the Arctic: acoustic tracking of floats and gliders, acoustic 1443 communication links, ice-tethered profilers and listening/telemetry/sound source 1444 stations, ice thickness measurements from floats, animal-borne sensors, and upward-1445 looking sonar and current meter moorings. However, the challenges are significantly 1446 greater in the Antarctic. The area of the Antarctic sea ice pack is much greater than 1447 that of the Arctic; many areas are more remote; and the divergence and strong 1448 seasonality of the sea ice pack makes ice-tethered stations more difficult to maintain. 1449 Therefore, in the Antarctic efforts will need to focus on one or more “well-measured” 1450 regions or basins. 1451 1452 Recommendations: Maintain the array of sound sources and acoustically-tracked 1453 floats established in the Weddell Gyre during the IPY (Figure 29). Establish a similar 1454 system in the Ross Sea Gyre. Expand the deployment of ice-capable floats (e.g. the 1455 Polar Profiler) and Ice Tethered Profilers in the Antarctic sea ice zone. Maintain and 1456 enhance the deployment of sensors on animals that forage in the sea ice zone. 1457

1458

1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474


47

Figure 29: Array of sound sources being used to track profiling floats in the Weddell 1475 Sea during the IPY (upper plot) and temperature and velocity field derived from 1476 profiling float data (E. Farhbach, pers. comm.). These measurements need to be 1477 sustained to extend the global array of profiling floats to the ocean beneath the sea 1478 ice. A similar array is needed to sample the Ross gyre. 1479 1480 Sea level: Tide gauges on the Antarctic continent contribute to monitoring of the 1481 Antarctic Circumpolar Current (e.g. Hughes et al., 2003; Meredith et al., 2004) as 1482 well as sea level, by contributing to the Global Sea Level Observing System (GLOSS, 1483 Figure 30). Three stations on the Antarctic Continent and several from islands and 1484 extreme southern points of continents are currently contributing in near-real time to 1485 the system in the Southern Ocean. 1486 1487 Recommendations: Maintain and expand the Southern Ocean GLOSS network, 1488 including increasing the number of stations reporting in real time. Install coastal tide 1489 gauges in the data-sparse Amunsen Sea sector. 1490 1491

1492 1493 1494 Figure 30: Status of the Global Sea Level Observing System (GLOSS) in October 1495 2009. Green dots = "Operational" stations for which the latest data is 2005 or later; 1496 yellow = "Probably operational" stations for which the latest data is within the period 1497 1995-2004; orange = "Historical" stations for which the latest data is earlier than 1498 1995; red = Stations for which no PSMSL data exist. 1499 1500 Basal melting and freezing 1501 Basal melting and freezing on the undersides of floating ice shelves exert significant 1502 influences on the ocean close to the Antarctic margin. These processes impact 1503 strongly on shelf water characteristics and the dense precursors of AABW in locations 1504 such as the southern Weddell and Ross Seas (e.g. Nicholls and Jenkins, 1993; 1505 Nicholls and Makinson, 1998). Freshening of AABW observed in the Indian and 1506 Pacific Sectors of the Southern Ocean has been attributed to enhanced basal melt 1507 (Jacobs et al., 2002; Jacobs, 2004, 2006; Rintoul, 2007). In West Antarctica, a marked 1508 deflation of parts of the ice sheet has been observed, ascribed to increased ocean 1509 temperatures impacting strongly on the ice shelves (e.g. Shepherd et al. 2004; Jenkins 1510 et al., 2010). However, despite their importance, ocean circulation and properties 1511 under shelf ice has been measured in only very few locations. Recent measurements 1512 beneath the Pine Island Glacier using the AUV Autosub are an exciting development, 1513 but sustained measurements are also needed, to track the impacts of ocean climate 1514


48

changes on the ice shelves, and the subsequent feedbacks. 1515 1516 Recommendations: Deploy and maintain oceanographic moorings beneath the 1517 Antarctic ice shelves in key strategic locations using hot water drilling technology 1518 (Figure 31). Coordinate work with the geological science community, where 1519 appropriate, to take advantage of drilling expeditions being conducted for studies of 1520 sediments and the sub-seabed. Establish moored arrays and repeat hydrographic 1521 sections near the ice front of key ice shelves to monitor inflow and outflow from the 1522 sub-ice cavity. 1523

1524

1525 1526 Figure 31: White circles indicate location of current or planned drill holes through 1527 ice shelves, allowing sampling of underlying ocean waters. 1528 1529 Enhanced meteorological observations 1530 An enhanced atmospheric observing system is needed to improve Antarctic and 1531 southern hemisphere weather forecasts. The enhanced observations should include 1532 additional automatic weather stations and remote profilers, sea level pressure 1533 observations from ice and ocean drifters, and aircraft (manned and un-manned). 1534 Climate research benefits from improved weather forecasts in the increased accuracy 1535 of the flux products derived from Numerical Weather Prediction model reanalyses. 1536 The air-sea fluxes of heat and moisture are poorly known at high southern latitudes, 1537 making it difficult to diagnose the interactions between atmosphere, ocean and sea ice 1538 that lie at the heart of climate variability and change. 1539 1540 Recommendations: State-of-the-art meteorological sensors (e.g. Improved 1541 Meteorology (IMET) systems) should be installed on additional Antarctic research, 1542 supply and tourist ships to provide validation data for the next generation of flux 1543


49

products from reanalyses and satellites. Deployment of surface flux reference stations 1544 is a significant technical challenge in the strong current, high wind and sea state 1545 environment typical of the Southern Ocean, but is required to provide a data set to test 1546 flux products derived from satellite data and reanalyses. The recently deployed air-1547 sea flux mooring in the Subantarctic Zone south of Tasmania is an important 1548 development (Figure 32); similar moorings are being planned for higher latitudes 1549 south of Australia, in the southeast Pacific, in the Argentine Basin, and in the Agulhas 1550 Return Current region. 1551 1552

1553 1554 1555 Figure 32: Air-sea flux mooring deployed at 47°S, 140°E south of Tasmania as part 1556 of Australia’s Integrated Marine Observing System (IMOS). This is the first air-sea 1557 flux mooring so far deployed in the Southern Ocean and will be used to assess the 1558 quality of air-sea flux products derived from satellites and reanalysis products. 1559 [Source: http://imos.org.au] 1560 1561 Phytoplankton, primary production and microbial processes 1562 Sustained observations of biomass, primary production and species distributions of 1563 phytoplankton and protozoa are needed to relate environmental variability (including 1564 sea ice) to biological activity. Ocean colour satellites are critical as they provide the 1565 only circumpolar view of biological activity in the Southern Ocean. In situ 1566 measurements are needed to refine algorithms used to interpret the satellite data, to 1567 relate surface chlorophyll to column-integrated production and for analysis of 1568 additional pigments and phytoplankton community composition. 1569 1570 Recommendations: Chlorophyll fluorescence, fast repetition rate fluorometry 1571 (FRRF), transmissometry, ocean colour and pigment analyses are needed on a larger 1572 suite of underway vessels (research, supply and tourist ships) supplemented by regular 1573 sampling for microscopic identification of species. These observations should also be 1574 made in the upper ocean on each of the repeat hydrographic transects; fluorescence is 1575 now being measured with seal tags as well. Such measurements should follow 1576 recommended procedures for calibration/validation of ocean colour by remote sensing 1577 (see below). Phytoplankton assemblages should be identified as closely as possible to 1578 species level and primary production rates measured using conventional 14C 1579 techniques, or using oxygen electrodes, during repeat transects by science vessels. 1580 Total particulates should be measured by transmissometry and/or underway flow 1581 cytometry. Unlike fluorometry, this measurement is not subject to photoinhibition and 1582


50

includes stocks of phytoplankton, protozoa, bacteria and detritus (i.e. the food 1583 available for grazers), complementing the other measurements. These data will enable 1584 the use of remote sensing data to quantify CO2 fluxes and ecological responses to 1585 change at basin scales. 1586 1587 Zooplankton and micronekton 1588 Mid-trophic level organisms (zooplankton, fish and squid) play a critical role in 1589 Southern Ocean ecosystems by transferring biomass and energy from primary 1590 producers to predators. However, despite their huge biomass and function in 1591 ecosystems and biogeochemical cycling, these organisms are poorly observed. They 1592 may also be particularly sensitive and vulnerable to climate change. Global warming 1593 will affect sea ice patterns and plankton distributions. Increased UV levels, ocean 1594 acidification, geographic shifts in species composition, invasive plankton species, 1595 pollution and harvesting impacts may also drive changes in mid-trophic levels with 1596 implications for both carbon cycling and top predators. Zooplankton sampling has in 1597 the past largely been carried out as part of focused, short-term experiments and has 1598 generally focused on distribution and abundance. Existing long-term sampling 1599 programs include the Japanese Antarctic Research Expedition (JARE) annual Norpac 1600 plankton net sampling, the US Antarctic Marine Living Resources (AMLR) program, 1601 the Palmer LTER (Waters and Smith, 1992), the British Antarctic Survey monitoring 1602 programme and the SCAR Southern Ocean Continuous Plankton Recorder (SO-CPR 1603 Survey, Figure 33). Gaps include a lack of winter data, lack of sampling in the sea ice 1604 zone, lack of data from the Pacific, and a lack of sampling at depths greater than 200 1605 m. The CPR, the primary tool used for broad-scale sampling of zooplankton, samples 1606 the top 20 m. 1607 1608 Acoustic approaches have great potential for sampling of mid-trophic levels (Figure 1609 34). The contribution that automated acoustic systems can make to the sustained 1610 observing system is summarised in Handegaard et al. (2010). Systems are being 1611 designed suitable for deployment on ships, moorings and drifting platforms. 1612 1613 Recommendations: Maintain and expand the CPR survey, in particular to fill gaps in 1614 the Pacific and Atlantic sectors and in winter. Use results from regional studies to 1615 design a zooplankton sampling plan that combines the broad spatial and temporal 1616 coverage of the CPR with other techniques (net tows, acoustics) to fill gaps and assess 1617 potential biases (e.g. summer sampling, CPR limited to top 20 m). Expand the use of 1618 automated acoustic techniques to sample the mid-trophic levels (Handegaard et al., 1619 2010). 1620 1621


51

1622 Figure 33: Location of CPR tows completed between 1991 and 2008. 1623 1624 1625 1626

1627 Figure 34. Demonstration of basin scale distribution and abundance of mid-trophic 1628 organisms provided by calibrated ships of opportunity (fishing vessels) over multi 1629 year time frame using well established standardized technologies and methodologies 1630 (Fig. 4 from Kloser et al., 2009). These basin scale snapshots provide information for 1631 ecosystem model parameterization, data assimilation and as an ecological indicator 1632


52

of change in the deep scattering layer over basin scales. Implementation of this 1633 method is very cost effective and forms a component of the necessary global coverage. 1634

1635 1636

Ecological monitoring via Top Predators 1637 Observations of the distribution and abundance of top predators (fish, penguins, sea 1638 birds, seals and whales) can provide indications of changes in the ecosystem as a 1639 whole. Long-term ecological monitoring programmes have been established at a few 1640 sites around Antarctica, including the Long Term Ecological Research (LTER) site on 1641 the western Antarctic Peninsula. The Commission for the Conservation of Antarctic 1642 Marine Living Resources (CCAMLR) also monitors land-breeding marine predators 1643 (seals, penguins and seabirds) at a number of sites under the CCAMLR Ecosystem 1644 Monitoring Programme (CEMP). The CEMP sites are located in three Integrated 1645 Study Regions in the South Shetland Islands, South Georgia and Prydz Bay (Agnew, 1646 1997). Although CEMP was established to monitor fisheries impacts, the long term 1647 time series are now also providing insights into ecosystem processes (e.g. Ballerini et 1648 al. 2009, Emmerson and Southwell 2008). The U.S. AMLR programme in the South 1649 Shetland Islands offers an excellent example of a long term time series where ship 1650 based oceanographic measurements have been made every year since 1986 along with 1651 colony based measurements of the population status and foraging behaviour of fur 1652 seals and penguins since 1998. Through these programs and others studies, significant 1653 changes in penguin populations have been observed in some regions (e.g. Ducklow et 1654 al., 2008; Weimerskirch et al., 2003), particularly on the western peninsula where the 1655 most dramatic environmental changes have been observed in recent decades. 1656 However, monitoring of top predators is limited in many parts of Antarctica. 1657 Enhanced development and application of platforms, technologies and survey 1658 methods will be crucial to establishing a broader network of monitoring for top 1659 predators. Furthermore, in many cases there is a lack of simultaneous physical and 1660 biogeochemical data, and information on lower trophic levels, to allow the causes of 1661 observed changes in higher trophic levels to be determined. 1662

The Tagging of Pacific Pelagics Programme (TOPP) (Block et al., 2002), is an 1663 excellent example of the type of integrated multi-species tracking programme that 1664 could be achieved under SOOS (see http://www.topp.org/). The power of such an 1665 approach is that combining at-sea movements of many individuals from multiple 1666 species enables identification of regions and marine features that are of most 1667 importance to the community of predators (i.e. ecologically significant areas, or 1668 ESAs). Different species employ different foraging and breeding strategies; by using 1669 a number of species, different aspects of the Southern Ocean environment can be 1670 monitored. Equally importantly, when this is conducted over a multi-year time frame, 1671 the dynamics of the system can be quantified. 1672

Table 4. List of species used to observe Ecologically Significant Areas. For each 1673 species the important ecological characteristics are listed as well as the most 1674 appropriate method of tracking. 1675

Species Prey Habitat

Max. dive depth (m)

Device*


53

Southern elephant seal†

squid, fish pelagic 1900 CTD

Adélie Penguin † krill pack ice 160 GLS

Emperor Penguin † squid, fish

fast ice

600 GLS

Antarctic Petrel † krill, amphipods, fish

pelagic 5 GLS

Antarctic Fulmar krill, amphipods, fish

pelagic 5 GLS

Snow Petrel krill, squid, fish pelagic 5 GLS Cape Petrel Short-tailed shearwater (summer only)

krill, fish (?) pelagic 50 GLS

Weddell seal † fish fast ice

pelagic 900 Argos

*Device types include Conductivity-Temperature-Depth recorders (CTD), Argos 1676 PTTs (Argos) and light temperature loggers (GLS). 1677

†Denotes core species which will be studied at multiple locations. 1678

1679 Recommendations: Establish and maintain multi-species tracking studies of key 1680 Antarctic predators to identify areas of ecological significance. Maintain existing 1681 long-term monitoring programs and extend monitoring to regions where little activity 1682 currently occurs. Assess the benefit of enhancing the physical and biogeochemical 1683 observing system in the vicinity of long-term monitoring sites to add value to 1684 ecological time series. Surveys of crab eater seal populations every 5 years should be 1685 conducted in regions where a baseline exists, to detect changes in abundance. 1686 1687 Benthos: The benthos is an important but generally poorly understood component of 1688 the Antarctic marine ecosystem and biodiversity. Antarctic benthic communities 1689 show high levels of endemism, gigantism, slow growth, longevity, late maturity, and 1690 adaptive radiations that generated considerable biodiversity in some taxa (Clarke & 1691 Johnston, 2003). Studies of these communities are therefore relevant to 1692 understanding the effect of global changes in the marine environment. Recent studies 1693 suggest some benthic organisms may be particularly sensitive to environmental 1694 changes (e.g. Peck et al., 2006) and to human disturbance (Stark et al., 2003). The 1695 effects of ocean acidification will be felt first in the cold, sub-surface waters in polar 1696 regions and therefore may have a significant impact on the benthos. Sustained 1697 observations of the distribution, abundance and diversity of benthic organisms are 1698 needed to determine the sensitivity of the benthic communities to climate and other 1699 changes. This information is particularly important to inform conservation and 1700 management decisions. 1701 1702


54

Recommendations: A number of recent programmes provide good examples of the 1703 integrated multidisciplinary benthic studies required (Snape et al. 2001, Stark et al. 1704 2003, Clarke et al. 2008, Montone & Weber in press; Sicinski et al. submitted, Smith 1705 et al. 2008, Brandt et al. 2004, Brandt et al. 2007; Gutt 2007, Gutt et al. 2007). These 1706 studies have used a variety of tools, including benthic landers with sediment traps and 1707 time-lapse photography and physical sensors; seafloor video surveys; coring; and 1708 targeted trawling. Sustained benthic observatories using these approaches should be 1709 established at a number of locations around Antarctica, including regions of rapid 1710 change (the Antarctic peninsula), areas where future change is expected (the 1711 Amundsen and Bellingshausen Seas), and more stable environments (East 1712 Antarctica). Sampling sites should be representative of the Antarctic shelf, 1713 continental slope and deep-sea. The biological observations need to be integrated 1714 with changes in the physical and chemical environment. 1715

1716 Remote sensing: Remote sensing has a particularly crucial role to play in remote 1717 regions like the Southern Ocean, where in situ observations will always be sparse. 1718 However because of the electromagnetic opacity of the seawater, satellite data are 1719 restricted to near-surface properties – such as skin temperature, surface elevation, 1720 ocean colour, and surface roughness. Satellite data have the unique advantage of 1721 showing the “big picture” of the large-scale ocean circulation while at the same time 1722 providing the “regional details” necessary to capture the very energetic mesoscale 1723 eddies. 1724 1725 High-precision, continuous satellite altimetry missions (Jason, Envisat, Sentinel), in 1726 full synergy with satellite gravity missions (GOCE, GRACE, Mitchum et al., 2001; 1727 Le Traon et al., 2001), play a vital role in monitoring surface elevation relative to the 1728 geoid, which to a large extent controls the large-scale depth-integrated circulation 1729 (Wunsch, 1996). Absolute current velocities can also be inferred from these sea 1730 surface height data (Johannessen et al., 2001). Scatterometers enable derivation of 1731 surface winds over open seawater (Millif et al., 2001). Infrared and microwave 1732 radiometers, including active and passive microwave sensors, measure SST 1733 (Reynolds, 2001), sea ice extent and motion (Drinkwater et al, 2001). Ocean colour 1734 measurements provide estimates of phytoplankton biomass in surface waters, primary 1735 production rates and some indication of community composition. 1736 1737 Satellite ocean colour measurements will be crucial for providing synoptic views of 1738 phytoplankton distribution, extending measurements from ships of opportunity, and 1739 allowing detection of possible changes in distribution as a result of climate change. It 1740 is vital that these measurements should be supported by an active 1741 calibration/validation programme that allows remotely sensed ocean colour data to be 1742 converted to chlorophyll estimates, and which allows possible changes in biomass to 1743 be distinguished from changes in atmospheric interference due to climate change. 1744 This will require measurements of surface chlorophyll, hyperspectral incoming 1745 radiation and ocean colour, and coloured dissolved organic matter (CDOM) to allow 1746 development of improved algorithms. Targeted research cruises will be required to 1747 develop models of the relationships between surface colour and subsurface 1748 chlorophyll maxima. 1749 1750 Remote sensing of the Southern Ocean region encounters some unique challenges. 1751 Persistent cloud cover limits the coverage obtained by infrared and visible band 1752


55

sensors. Combining data from multiple sensors, such as the Jason and ENVISAT 1753 altimeters or the NASA and ESA SST sensor suites, provides more complete 1754 coverage at high latitudes. A combination of different types of information, such as 1755 infrared and microwave data for measuring SST, is also useful, and in situ 1756 measurements for removal of biases are particularly important at high latitudes 1757 (Reynolds, 2001). To optimise their orbits to avoid aliasing tides, many of the satellite 1758 altimeters are in orbits that do not go poleward of 66 degrees (e.g. Jason). For SST, 1759 ocean colour and wind speed, large data or algorithm dropouts occur as the satellite 1760 approaches the ice. There is a need to investigate better algorithms and corrections 1761 near the critical ocean/sea ice/continent interface in order to extend the sea surface 1762 height and wave height measurements close to Antarctica. Tide gauges around the 1763 coast of Antarctica are therefore important for extending measurements of sea level to 1764 the coast (Mitchum et al., 2001). Agreements for the scientific use of new, higher 1765 spatial resolution visible-IR datasets, many of which are currently expensive, would 1766 be desirable, particularly as these datasets build up multi-annual coverage. Improved 1767 sensors/algorithms for sea ice extent, concentration, volume and motion are a high 1768 priority (Drinkwater et al., 2001). The small Rossby radius in polar regions means that 1769 satellite remote sensing products need to be produced at a higher resolution than 1770 required at lower latitudes, but also means that remotely sensed data are all the more 1771 critical for setting hydrographic sections or moorings in the context of the local 1772 mesoscale eddy field. 1773 1774 Recommendations: To ensure continuity of satellite data and maintain the quality of 1775 data interpretation through in situ validation measurements. The suites of in situ 1776 measurements proposed within the SOOS programme naturally provide data for 1777 ground-truthing and algorithm improvements for each of the remote sensing data 1778 streams mentioned above. In particular, high priority platforms for SOOS include 1779 high-precision satellite altimetry missions (Jason, Envisat, Sentinel), in full synergy 1780 with satellite gravity missions (GOCE, GRACE); scatterometers for wind stress; 1781 microwave and infrared instruments for SST; cryospheric satellites; and ocean colour. 1782

Southern Ocean Climate and Ecosystem Information System: The SOOS vision 1783 includes not just the collection of sustained observations, but the delivery of Southern 1784 Ocean information to a wide range of users. SOOS will coordinate and provide 1785 access to analyses and data syntheses that add value to the raw information. These 1786 services might include maps of ocean properties (e.g. ocean heat and salt content, sea 1787 ice conditions, or measures of biological productivity) or time series (e.g. changes in 1788 pH, sea level, or surface biomass). At present, such products are produced by many 1789 groups around the world, but it is difficult and time-consuming to locate and access 1790 material from multiple sources, particularly across disciplines. 1791 1792 Recommendations: SOOS should facilitate the development of a system to provide 1793 seamless access to a wide range of data products for the Southern Ocean, guided by 1794 the needs of research users. 1795 1796

3.3Complementaryresearch1797

1798 SOOS has a clear focus on sustained ocean observations. Many other activities, 1799 including sustained observations in the atmosphere and cryosphere, process studies, 1800


56

and modelling, are required to address the science challenges motivating the SOOS. A 1801 few examples of research activities that complement the core SOOS mission are noted 1802 here. 1803 1804 Atmospheric trace gas observations: One of the key questions motivating the SOOS 1805 is the sensitivity of the Southern Ocean carbon cycle to climate change. The SOOS 1806 observations of ocean carbon need to be complemented by monitoring of the lower 1807 atmosphere for a range of gases, including CO2, O2/N2 and related tracers. Both 1808 airborne sampling and land-based flask and continuous monitoring stations are 1809 required. 1810 1811 Ice cores from high accumulation rate coastal regions: The short duration of the 1812 instrumental record poses a huge challenge when attempting to understand Southern 1813 Hemisphere climate variability and change. Ice cores from high accumulation rate 1814 coastal sites will be of immense value in reconstructing a record of past change on 1815 time scales from years to millennia (e.g. Curran et al., 2003; Goodwin et al., 2004). 1816 1817 Sediment cores: New sediment cores from medium to high accumulation rate regions 1818 will help to identify changes in Southern Ocean circulation and structure during the 1819 course of past glacial cycles. These cores will provide estimates of past changes in sea 1820 ice extent and shifts in ocean fronts, and help to clarify the relationship between 1821 changes in the northern and southern hemispheres. 1822 1823 Process studies: Some of the key unknowns regarding the role of Antarctica and the 1824 Southern Ocean in the global climate system require focused process studies to be 1825 resolved. Generally, smaller scale processes associated with submesoscale eddies, 1826 internal waves, surface waves etc. are poorly represented in climate models and 1827 process studies meant to refine parameterizations are important. In the Southern 1828 Ocean context, such processes can exert a control on, for example, mixed layers, 1829 upwelling and productivity, the extent of warm water melting the glacial ice, and thus 1830 their consequences on the climate system may be large. Exchange of water masses 1831 across the Antarctic Slope Front is an important, but poorly understood, process in the 1832 formation of dense water on the continental shelf. The complex interactions between 1833 the ocean and ice shelves, including melting near the grounding line and formation of 1834 marine ice beneath the ice shelf, remain largely unobserved. These interactions are 1835 important to the freshwater balance, to water mass transformation, and to the stability 1836 of the ice sheets that feed the ice shelves. New technology to explore the ice shelf 1837 cavities is now available and expected to provide a significant step forwards. Progress 1838 in understanding what physical and biogeochemical processes control the rate of 1839 carbon export in the Southern Ocean will require process-oriented field experiments 1840 and biogeochemical time series measurements from moorings. 1841 1842 Ecological process studies. Regular observations from ships of opportunity will 1843 identify different bioregions, characteristic populations and seasonal successions. 1844 However certain parameters are not tractable from underway surface measurements, 1845 yet are crucial for estimates of food availability and carbon flux, and will require 1846 measurements from targeted research cruises if they are to be incorporated in models. 1847 These include structure of the deep chlorophyll maximum, diversion of primary 1848 production through consumption and respiration in the microbial loop, coupling of 1849 phytoplankton production to grazers, and export of carbon and biomass to the deep 1850


57

ocean. Ocean manipulation experiments and mesocosm studies are needed to 1851 examine hypotheses such as the role of iron in ecosystem production and to assess the 1852 impacts of ocean acidification 1853 1854 Integration of remotely sensed data from multiple sensors/platforms: Data 1855 integration from sensors measuring in similar E-M bands but at different spatial 1856 and/or temporal resolution would benefit greatly from the placement of a few 1857 automated moorings/ground stations on the ice shelf, above and below the ice/water 1858 within the seasonal sea ice zone and in open Southern Ocean waters. Such platforms 1859 are currently maintained at lower latitudes, for example at the BATS station and 1860 Aqua-Alta in Italy for ocean colour, but not in the high latitude Southern Ocean where 1861 ecological and physical conditions often lead to algorithm failure. 1862 1863 1864

4. Status and a roadmap for implementation of SOOS 1865

4.1SOOSasalegacyoftheInternationalPolarYear1866

1867 Many of the observations identified as “building blocks” of the SOOS in the previous 1868 section were completed during the IPY, during which the Southern Ocean was 1869 measured in a truly comprehensive way for the first time. IPY measurements spanned 1870 the circumpolar extent of the Southern Ocean, from the subtropical front to the 1871 Antarctic continental shelf. Most of the WOCE/CLIVAR repeat hydrographic 1872 sections were re-occupied, providing a near-synoptic snapshot of the physical and 1873 biogeochemical state of the Southern Ocean through the full water depth. Many 1874 properties, such as trace elements like iron, were measured throughout the water 1875 column for the first time. A similar snapshot, of a more limited set of parameters, 1876 took much of a decade to complete during WOCE. Argo floats collected more than 1877 60,000 temperature and salinity profiles during the 24-month IPY period, providing 1878 broad-scale, quasi-synoptic, year-round sampling of the upper 2 km of the Southern 1879 Ocean. Oceanographic sensors on marine mammals provided a similar number of 1880 profiles, including measurements from regions where traditional oceanographic 1881 instruments have difficulty sampling, such as the sea ice zone in winter. Moorings 1882 provided continuous time-series measurements of dense water overflows and 1883 boundary currents, major currents like the Antarctic Circumpolar Current and the 1884 Antarctic Slope Front, and coastal sea level. Many new species were discovered and 1885 new insights into processes influencing biodiversity and ecosystem structure and 1886 function were obtained. 1887 1888 Perhaps most importantly, the IPY activities spanned all disciplines of Southern 1889 Ocean science. Southern Ocean IPY demonstrated that an integrated, multi-1890 disciplinary, sustained observing system is feasible and urgently needed to address 1891 issues of high relevance to society, including climate change, ocean acidification and 1892 the future of the Southern Ocean ecosystem. 1893 1894

4.2StatusofSouthernOceanobservations1895

1896


58

Commitments have already been made to complete key elements of the SOOS. For 1897 example, most of the repeat hydrographic lines will be re-occupied within the next 1898 five years, consistent with the SOOS design (GO-SHIP). Several countries have long-1899 standing commitments to monitor Drake Passage with annual full-depth hydrography, 1900 more frequent sampling of the upper ocean, and moored instruments. Most of the 1901 underway observation network shown in Figure 22 has been in place for more than a 1902 decade and is expected to continue. Several moored arrays in the Weddell Sea have 1903 been maintained for a decade and are planned to continue. Similar programs are 1904 being established in other locations around Antarctica. Plans are well advanced for a 1905 comprehensive observing system in the South Atlantic ocean, the South Atlantic 1906 Meridional Overturning Circulation (SAMOC) experiment (Figure 35). 1907 1908 Programs like the Argo profiling float array and the MEOP network of tagged seals 1909 have helped to revolutionise our ability to observe the Southern Ocean. The science 1910 being done with these measurements has already had a significant impact on our 1911 understanding of the Southern Ocean. For these reasons, significant effort is being 1912 made to ensure these critical data sets are maintained and enhanced in future years. 1913 However, there is as yet no firm commitment to long-term sustained funding of these 1914 systems. 1915 1916 With regard to biological sampling, the Palmer LTER on the western Antarctic 1917 Peninsula has been in operation for 15 years and is expected to continue; the long-1918 term monitoring conducted by the CEMP program also has a long-standing 1919 commitment. A number of nations have committed to ongoing CPR transects across 1920 the Southern Ocean. The number and breadth of biological measurements being 1921 made from ships of opportunity is slowly growing. 1922 1923

1924 1925 Figure 35: The draft SAMOC array for the Atlantic sector of the Southern Ocean. 1926 1927


59

While the list of existing commitments provides some grounds for optimism and a 1928 firm foundation on which to build, there is substantial work to be done to secure the 1929 resources for a truly sustained and comprehensive observing system in the Southern 1930 Ocean. Many of the challenges (e.g. the lack of sustained funding and the need for 1931 improved sensors) are common to the global ocean observing system as a whole. 1932 Major gaps include: 1933

• sustained funding for most elements of the SOOS 1934 • observations below the sea ice 1935 • biological and biogeochemical sampling in winter and at large scales 1936 • lack of time series data, particularly for biology and biogeochemistry 1937 • inadequate integration of physics, biology and biogeochemistry observations 1938 • sparse sampling of the deep ocean 1939

Almost all elements of the observing system require enhancement to reach the 1940 sampling required to address the key scientific challenges. Figure 36 summarises the 1941 status of the Southern Ocean observing elements monitored by JCOMMOPS for the 1942 month of June 2010, illustrating that substantial gaps remain, particularly in winter. 1943 1944

1945 1946 Figure 36: Status of the Southern Ocean observing system for the month of June 1947 2010, for a set of platforms monitored by JCOMMOPS. The ship coverage is more 1948 complete in the summer months, but even in that season substantial gaps remain. 1949

4.3Nextstepstowardsimplementation1950

1951 a.) Scientific Coordination 1952 1953 Two panels have shared responsibility for oversight of SOOS during its development 1954 stage: the Expert Group on Oceanography co-sponsored by SCAR and SCOR, and 1955


60

the Southern Ocean Implementation Panel co-sponsored by CLIVAR, CliC and 1956 SCAR. The Expert Group has an explicit focus on integrating across disciplines in 1957 Southern Ocean research, while the CLIVAR/CliC/SCAR panel addresses physical 1958 and biogeochemical aspects of the Southern Ocean climate system. Shared 1959 membership on these two panels has ensured effective coordination between the 1960 panels and across international programs spanning the disciplines of Southern Ocean 1961 research. 1962 1963 As we move towards implementation of SOOS, it is necessary to identify a single 1964 group with lead responsibility for SOOS. The SCAR/SCOR Expert Group, with its 1965 focus on interdisciplinary observations, is the logical choice given the broad scope of 1966 SOOS. The CLIVAR/CliC/SCAR Southern Ocean panel must continue to be closely 1967 involved, particularly in helping to refine the design of the physical and 1968 biogeochemical components of the observing system. A number of other panels and 1969 national and international programs also have an important role to play, as outlined 1970 below. 1971 1972 A program of the scale and complexity of the SOOS requires a Program Office or 1973 Secretariat. The role of the Program Office will be to serve as a central contact point 1974 for SOOS, to monitor progress towards SOOS goals, to facilitate coordination of field 1975 work, to assist in the organisation of workshops and synthesis activities, and to 1976 coordinate a web site and other activities to advertise the aims and achievements of 1977 the SOOS. 1978 1979 b.) Observing system design 1980 1981 For many elements of the SOOS, the optimal sampling plan has not yet been 1982 determined. Quantitative studies of the trade-offs to be made between observing 1983 system elements are needed, using a variety of approaches including formal 1984 Observing System Experiments (OSEs). For each element of the SOOS, a 1985 quantitative target for the number and frequency of observations needs to be defined, 1986 so the progress towards implementation of SOOS can be assessed. For some elements 1987 of SOOS, these requirements have been defined (e.g. repeat hydrography, Argo, 1988 surface drifters, and ice drifters). For others, including many of the biological 1989 parameters, further work is required. This task should be overseen by the 1990 SCAR/SCOR Expert Group on Oceanography, in consultation with others. 1991 1992 In the case of the global climate module of GOOS, having clear numerical targets for 1993 numbers of observing platforms monitoring ‘Essential Climate Variables’ reported to 1994 the United Nations Framework Convention on Climate Change (UNFCCC) has 1995 proven extremely useful for brokering multi-governmental support required to sustain 1996 the system. Governments have shown themselves willing to sign up to clear, simple 1997 numerical implementation targets that are backed up by solid research. To achieve 1998 broad intergovernmental support to sustain a SOOS, progress towards SOOS goals 1999 should be monitored in a process analogous to that currently employed for the global 2000 climate module of GOOS. 2001 2002 2003 c.) New technology 2004 2005


61

Present tools are not adequate to answer the key science questions motivating SOOS, 2006 so SOOS will need to advocate for and adopt new technologies. Examples include 2007 the development of new low-power, stable biological and biogeochemical sensors for 2008 deployment on a variety of fixed and mobile platforms; long-duration, inexpensive 2009 moorings to allow continuous broad-scale sampling; and floats and gliders with 2010 expanded capability in terms of depth, range and sensors. These needs are not unique 2011 to the Southern Ocean and SOOS will need to be well-integrated with technological 2012 developments relevant to the global observing system. 2013 2014 d.) Building of partnerships 2015 2016 As appreciation of the role of the Southern Ocean in global climate, biogeochemical 2017 cycles and marine productivity has grown, so has interest from the research 2018 community. The number of national and international research programs with a focus 2019 on the Southern Ocean has therefore also grown. The success of SOOS will depend 2020 on effective integration and coordination of these efforts. The Southern Ocean is a 2021 vast and remote domain and the logistical resources available for its study are 2022 relatively limited. This places a further imperative on effective coordination of 2023 research between nations and across disciplines. 2024 2025 Recent initiatives of particular relevance to SOOS include: 2026

• SCAR’s programme on Antarctica and the Global Climate System (AGCS) is 2027 a major research programme to investigate the nature of the atmospheric and 2028 oceanic linkages between the climate of the Antarctic and the rest of the Earth 2029 system, and the mechanisms involved therein. The scientific direction of the 2030 project is overseen by the AGCS Steering Committee. The programme makes 2031 use of existing deep and shallow ice cores, satellite data, the output of global 2032 and regional coupled atmosphere-ocean climate models and in-situ 2033 meteorological and oceanic data to understand the means by which signals of 2034 tropical and mid-latitude climate variability reach the Antarctic, and high 2035 latitude climate signals are exported northwards. AGCS will help define the 2036 SOOS requirements for understanding physical climate, and provide a link 2037 between the ocean focus of SOOS and climate research in the atmosphere and 2038 cryosphere. 2039

• The Southern Ocean Sentinel aims to assess the impacts of climate change on 2040 Southern Ocean marine ecosystems. The Sentinel program has a strong 2041 emphasis on modelling as well as observations (both process studies and 2042 sustained observations). The Southern Ocean Sentinel programme has a 2043 significant role to play in refining the design of the ecosystem component of 2044 the SOOS. 2045

• Integrating Climate and Ecosystem Dynamics in the Southern Ocean (ICED) 2046 is a multidisciplinary circumpolar ecosystem programme. Established by a 2047 group of polar scientists from around the world representing a wide range of 2048 research areas, ICED will facilitate the scientific coordination and 2049 communication required to undertake integrated circumpolar analyses of 2050 Southern Ocean ecosystems. Over the next decade, ICED will address the 2051 need to increase our understanding of circumpolar ecosystem operation in the 2052 context of large–scale climate processes; local–scale ocean physics; 2053 biogeochemistry; food web dynamics; and harvesting. ICED is being 2054 developed as a joint programme of IMBER and GLOBEC and is closely 2055


62

linked with EUR–OCEANS. Like the Sentinel programme, ICED can make a 2056 major contribution to SOOS by defining and implementing the sustained 2057 observations needed to understand Southern Ocean ecosystems and their 2058 response to climate and other forcing. 2059

• The Southern Ocean Carbon, Ecosytems and Biogeochemistry (SOCEB) 2060 programme under development in the USA is also of direct relevance to 2061 SOOS. This initiative recognises that the most pressing issues in Southern 2062 Ocean research require much closer integration of the Southern Ocean 2063 biogeochemistry and ecosystem research communities. The goals of SOCEB 2064 are closely aligned with those of the SOOS plan. The SOCEB community will 2065 make a substantial contribution to SOOS by defining the role of sustained 2066 observations in addressing critical science questions at the interface of 2067 physics, biogeochemistry and ecology. 2068

• The Antarctic Sea ice Processes and Climate (ASPeCt) program has the 2069 objectives to determine the spatial and temporal variability of the basic 2070 physical properties of sea ice that are important to air-sea interaction and to 2071 biological processes within the Antarctic sea-ice zone and to understand the 2072 key sea-ice zone processes necessary for improved parameterisation of these 2073 processes in coupled models. 2074

2075 e) International context for the SOOS 2076 2077 The SOOS is currently sponsored and/or endorsed by SCAR, SCOR, CAML, GOOS, 2078 POGO and WCRP. A SOOS is envisioned to operate in much the same way as a 2079 regional component of the Global Ocean Observing System (GOOS). Climate 2080 relevant components of the GOOS, and hence SOOS, are implemented by Member 2081 States cooperating through the IOC/WMO Joint Commission for Oceanography and 2082 Marine Meteorology (JCOMM) and contribute to the Global Climate Observing 2083 System (GCOS) and the Global Earth Observing System of Systems (GEOSS). 2084 Processes in the Southern Ocean affect climate on the global scale and over a range of 2085 time scales. JCOMM is already aiding in the development of SOOS, and at the 2086 appropriate time the SOOS supporters will seek formal endorsement by and 2087 involvement of JCOMM. Several of the elements of the SOOS are already operating 2088 under JCOMM oversight in the Southern Ocean and elsewhere (such as the tide gauge 2089 network of GLOSS, the Argo float program, and the International Programme of 2090 Antarctic Buoys – IPAB). 2091 2092 The Member States of the Intergovernmental Oceanographic Commission (IOC) of 2093 UNESCO, the World Meteorological Organization (WMO) and other relevant bodies, 2094 including the Parties to the Antarctic Treaty Consultative Mechanism (for areas south 2095 of 60oS), will be asked to formally endorse the SOOS and its network design in order 2096 to catalyze the intergovernmental support that is required to achieve a specific set of 2097 operational targets and to maintain operations for the long term. The 132 Member 2098 States of the Intergovernmental Oceanographic Commission have already resolved to 2099 work towards development of a SOOS (Report of the IOC Executive Council XLI 2100 ,2008) demonstrating the widespread interest in the SOOS and increasing confidence 2101 that the proposed network will be implemented and sustained. 2102 2103 While the Antarctic Treaty itself is concerned mostly with the continent of Antarctica 2104 and its ice shelves, its Protocol on Environmental Protection to the Antarctic, which 2105


63

entered into force in 1998, encompasses several environmental issues relevant for the 2106 Southern Ocean. The SOOS may be in a position to meet a significant portion of 2107 requirements of the Protocol, the Convention for the Conservation of Antarctic 2108 Marine Living Resources (1982), the Convention for the Conservation of Antarctic 2109 Seals (1972), and environmental protection measures in Antarctica and surrounding 2110 waters. The development of a SOOS meets the initial requirements of ATCM 2111 Resolution 3 (2007), which welcomed and supported “the proposal by SCAR to 2112 establish a multi-disciplinary pan-Antarctic observing system, which will, in 2113 collaboration with others, coordinate long-term monitoring and sustained observation 2114 in the Antarctic”, and which recommended “that the Parties: 2115 2116

1. urge national Antarctic programmes to maintain and extend long-term 2117 scientific monitoring and sustained observations of environmental change in 2118 the physical, chemical, geological and biological components of the Antarctic 2119 environment; 2120 2121 2. contribute to a coordinated Antarctic observing system network initiated 2122 during the IPY in cooperation with SCAR, CCAMLR, WMO, GEO and other 2123 appropriate international bodies; 2124 2125 3. support long-term monitoring and sustained observations of the Antarctic 2126 environment and the associated data management as a primary legacy of the 2127 IPY, to enable the detection, and underpin the understanding and forecasting 2128 of the impacts of environmental and climate change.” 2129 2130

SOOS is a contribution towards achieving that recommendation. 2131 2132 As stated above, the SOOS will constitute a significant legacy of the IPY. In this 2133 context, it is noteworthy that the 60th Session of WMO Executive Council in June 2134 2008 endorsed the idea of an International Polar Decade, in recognition of the rapid 2135 rates of change in polar regions and the impact of high latitude change on the rest of 2136 the globe. The SOOS would make a major contribution to such an initiative, and 2137 (along with an Arctic Ocean Observing System) was called for in the IPY Design 2138 Plan. 2139 2140 While widespread support from international agencies and programmes is essential, 2141 ultimately much of the funding to support the SOOS will flow from individual 2142 nations. It is therefore necessary to build a coalition of national programmes with a 2143 strong commitment to the SOOS. 2144 2145 f) Transition to a sustained operational system 2146 2147 Implementing the SOOS implies eventual transition of sustained observations being 2148 carried out in the Southern Ocean into an operational data stream that is freely 2149 distributed in near real time as the operational Southern Ocean component of the 2150 Global Ocean Observing System. As for any regional ocean observing system, a first 2151 target is to sustain and expand the existing operational system components, so as to 2152 provide near-term tangible achievements, with a high likelihood of success, early in 2153 the development of the SOOS. 2154 2155


64

The Southern Ocean oceanographic research community is, and for many years will 2156 continue to be, both the primary provider and primary user of in situ ocean data. Thus, 2157 incorporating research community products into the observing system, and 2158 simultaneously designing the system to help address research community hypotheses, 2159 will be absolutely critical in ensuring we can monitor the Southern Ocean for the 2160 benefit of all, including operational organizations and their clients. The objective for a 2161 SOOS should thus be not to try to fully transition research observations into an 2162 operational system, but to better ensure that the wealth of research observations is 2163 maintained into the future, is counted as an integral component of the SOOS, and 2164 enters the SOOS data system in near real-time, so that the latter draws on all of the 2165 best observations being taken, irrespective of whether they are funded on a sustained 2166 or research basis. 2167

4.4Datastrategy2168

2169 For the SOOS to succeed, it is critical that a data system be established that ensures 2170 that both past and future data sets are accessible and of known quality, consistent with 2171 the SCAR Data and Information Management Strategy published in 2009. The SOOS 2172 strategy for managing data will be based on the following elements or principles: 2173 2174 1) Open access to SOOS data 2175 2176 SOOS will establish a data policy of unrestricted access as soon as feasible after data 2177 collection. The data policy will be established based on IPY, IOC and SCAR data 2178 policies and national and international legislation. The immediate, free access to 2179 Argo data provides a model. 2180 2181 2) Establish a SOOS data infrastructure 2182 A SOOS data portal will provide one-stop access to a distributed data archive holding 2183 all SOOS related data. The goal is to provide easy access to both historical and future 2184 data sets relevant to SOOS. At present, physical and biological data sets are often 2185 handled by separate data systems, making interdisciplinary research very difficult. In 2186 fact, what is required is a data infrastructure that includes a portal, as well as 2187 registries, protocols and standards, services, content, physical hardware and people. 2188 The European SeaDataNet project and the Australian Integrated Marine Observing 2189 System (IMOS) provide regional examples of the data infrastructure concept. An 2190 effective SOOS data infrastructure requires dedicated investment, just as any other 2191 component of SOOS infrastructure. 2192 2193 3) Use existing data centres where possible 2194 2195 SOOS will use a distributed data system model, where data are quality controlled and 2196 archived by data assembly centres. For physical and biogeochemical data, examples 2197 of highly effective data centres include the CLIVAR & Carbon Hydrographic Data 2198 Office (CCHDO), the thermal data assembly centres, and the Argo data system. For 2199 marine biodiversity data, the dataportal SCAR-MarBIN is an open-access repository. 2200 Established during the IPY, it houses over 1 million geo-referenced distribution 2201 records from 165 datasets. The register of some 16,500 taxa (of which 9,500 are 2202 verified species) includes DNA barcodes for 1,500 species. The information is served 2203 to the Encyclopaedia of Life, an online resource with an illustrated species on each 2204


65

page. National Antarctic Data Centres (NADCs) and National Oceanographic Data 2205 Centres (NODCs) will provide building blocks of the SOOS data system. 2206 2207 The SOOS data portal will streamline access to data sets held in the distributed 2208 archives. An important role for the SOOS will be to ensure that it is possible to 2209 identify, access and integrate the physical and biological data relevant for a particular 2210 study, even if the individual data sets are held in different data centres. 2211 2212 Where appropriate data centres do not exist, SOOS will work with established data 2213 centres to seek a solution to host these ‘orphan’ data types. The Polar Information 2214 Commons project of CODATA-IPY-SCADM is exploring novel approaches to tackle 2215 this problem. 2216 2217 4) Improve access to and quality of historical data 2218 2219 Given the lack of observations from the Southern Ocean, it is critical that historical 2220 data is accessible and of known quality. Efforts have been made to do this for some 2221 physical oceanographic data (e.g. the Southern Ocean Data Base of Orsi and 2222 Whitworth, 2005), and the recent compilation of zooplankton net tow data sets 2223 (KRILLBASE, Atkinson et al., 2008) demonstrates the value of this approach. SOOS 2224 will aim to foster similar efforts for data sets that have not yet been assembled in this 2225 way and to ensure compatibility and integration between data from different 2226 disciplines. 2227 2228 5) Foster a culture of good data management practices 2229 2230 The success of any data system depends ultimately on the willingness of investigators 2231 (and their funders) to take data management seriously. SOOS will aim to foster a 2232 culture where PIs take responsibility for ensuring their data reach data assembly 2233 centres in a timely manner and that metadata records are maintained. The possibility 2234 of appointing a SOOS Data Coordinator in the SOOS Project Office will be explored. 2235 The establishment of data coordinators for individual projects or cruises will be 2236 encouraged. 2237 2238 6) Establish protocols for data management and data exchange 2239 2240 The SOOS data portal will also foster agreements on protocols for data collection, 2241 data exchange, quality control and archiving, based on best-practice in individual 2242 disciplines. 2243 2244

4.5SOOSin10years2245

2246 The observations that are feasible now, with existing technology and resources, are 2247 not adequate to address the key science challenges and issues of societal relevance in 2248 the Southern Ocean. Year-round, full-depth, multi-disciplinary monitoring of the 2249 Southern Ocean will remain beyond our reach if we need to rely on existing tools. 2250 New technologies are needed, and many are already under development. 2251 2252


66

In ten years time, we envision an expanded SOOS that relies heavily on the use of 2253 autonomous sampling and includes: 2254 2255

• Profiling floats with additional biogeochemical sensors, depth range and 2256 longevity. 2257

• Cost-effective, long-term, moored time series stations, measuring velocity and 2258 water properties, and transferring data using data capsule technology and 2259 telemetry. 2260

• Gliders used routinely for monitoring key areas and water mass formation 2261 areas, including beneath the ice 2262

• Sea ice and snow thickness delivered on a routine basis from satellite sensors, 2263 well-calibrated against a decade of in situ studies. 2264

• Routine delivery of Southern Ocean state assessments and increasing use of 2265 reanalyses in the interpretation of observations. 2266

• Increased capability to observe the Southern Ocean developed in additional 2267 countries. 2268

• Development of affordable sensors for biology and biogeochemistry for use on 2269 moorings, gliders, marine mammals and floats 2270

• Moored arrays monitoring the major dense water overflows, outflows and 2271 shelf waters. Water sampling throughout year for physical and chemical 2272 properties from Antarctic bases 2273

• Deployment of chlorophyll a sensors, flow cytometers, and FRRF on floats 2274 and AUVs 2275

• Repeat sea ice transects every 30-60 degrees of longitude. 2276 • Comprehensive multi-disciplinary underway sampling of the circumpolar 2277

Southern Ocean from an expanded fleet of ships-of-opportunity. 2278

5. Conclusion 2279

The Southern Ocean influences climate, biogeochemical cycles and biological 2280 productivity on global scales. Many of the most difficult and pressing issues faced by 2281 society – climate change, sea-level rise, ocean acidification, and conservation of 2282 marine resources – cannot be addressed effectively without improved understanding 2283 of Southern Ocean processes and feedbacks and their sensitivity to change. The most 2284 urgent research challenges in the Southern Ocean often span disciplines. A Southern 2285 Ocean Observing System is needed to provide the sustained, integrated, multi-2286 disciplinary observations required to meet these challenges. 2287

2288

2289


67

Acronyms: 2289

2290 AABW Antarctic Bottom Water 2291 AAIW Antarctic Intermediate Water 2292 ACC Antarctic Circumpolar Current 2293 ADCP Acoustic Doppler Current Profiler 2294 AGCS Antarctica in the Global Climate System 2295 ATCM Antarctic Treaty Consultative Meeting 2296 AUV Autonomous Underwater Vehicle 2297 CAML Census of Antarctic Marine Life 2298 CASO Climate of Antarctica and the Southern Ocean (IPY project) 2299 CCAMLR Commission for the Conservation of Antarctic Marine Living 2300

Resources 2301 CCHDO CLIVAR Carbon and Hydrographic Data Office 2302 CliC Climate and the Cryosphere 2303 CLIVAR Climate Variability and Prediction Program 2304 CPR Continuous Plankton Recorder 2305 CTD Conductivity – Temperature – Depth (pressure) 2306 GOOS Global Ocean Observing System 2307 GCOS Global Climate Observing System 2308 GEOSS Global Earth Observing System of Systems 2309 GLOSS Global Sea Level Observing System 2310 ICED Integrated Climate and Ecosystem Dynamics 2311 IMBER Integrated Marine Biogeochemistry and Ecosystem Research 2312 IMOS Integrated Marine Observing System (Australia) 2313 IOC International Oceanographic Commission 2314 IPAB International Program for Antarctic Buoys 2315 IPY International Polar Year 2316 JCOMM Joint WMO-IOC Technical Commission for Oceanography and 2317

Marine Meteorology 2318 JCOMMOPS JCOMM in-situ Observing System Support centre 2319 JGOFS Joint Global Ocean Flux Study 2320 NADC National Antarctic Data Centre 2321 NOAA National Oceanographic and Atmospheric Administration 2322 NODC National Oceanographic Data Centre 2323 POGO Partnership for Observations of the Global Ocean 2324 SAMW Subantarctic Mode Water 2325 SASSI Synoptic Antarctic Shelf Slope Interaction (IPY project) 2326 SCADM SCAR Standing Committee on Antarctic Data Management 2327 SCAR Scientific Committee on Antarctic Research 2328 SCAR MarBIN SCAR Marine Biodiversity Information Network 2329 SCOR Scientific Committee on Oceanographic Research 2330 SO Southern Ocean 2331 SOCEB Southern Ocean Carbon, Ecosystems and Biogeochemistry 2332 WCRP World Climate Research Program 2333 WMO World Meteorological Organisation 2334 2335

2336


68

References 2336

2337 Ackley, S; Wadhams, P; Comiso, JC, et al., 2003. Decadal decrease of Antarctic sea 2338

ice extent inferred from whaling records revisited on the basis of historical and 2339 modern sea ice records. Polar Research, 22, 19-25. 2340

Agnew, 1997 2341 Ainley, D. G., E. D. Clarke, K. Arrigo, W. R. Fraser, A. Kato, K. J. Barton, and P. R. 2342

Wilson, 2005. Decadal-scale changes in the climate and biota of the Pacific 2343 sector of the Southern Ocean, 1950s to the 1990s. Antarctic Science 17:171-2344 182. 2345

Alley, RB; Marotzke, J; Nordhaus, WD, et al., 2003. Abrupt climate change. 2346 Science, 299, 2005-2010. 2347

Aoki, S., N. L. Bindoff, and J. A. Church. 2005a. Interdecadal watermass changes in 2348 the Southern Ocean between 30°E and 160°E. Geophysical Research Letters 2349 32:10.1029/2004GL022220. 2350

Aoki, S., Rintoul, S.R., Ushio, S., Watanabe, S. and Bindoff, N.L., 2005b. Freshening 2351 of the Adélie Land Bottom Water near 140°E. Geophysical Research Letters, 2352 32(L23601): 10.1029/2005GL024246. 2353

Arbic, B.K. and Owens, W.B., 2001. Climatic warming of Atlantic Intermediate 2354 Waters. Journal of Climate, 14: 4091-4108. 2355

Atkinson A, Siegel V, Pakhomov E, Rothery P (2004) Long-term decline in krill 2356 stock and increase in salps within the Southern Ocean. Nature 432:100-103. 2357

Atkinson, A.; Siegel, V.; Pakhomov, E. A., et al., 2009. A re-appraisal of the total 2358 biomass and annual production of Antarctic krill. Deep-Sea Research Part I 2359 Oceanographic Research Papers, 56, 727-740. Article Number: 2360 10.1016/j.dsr.2008.12.007 2361

Ballerini T, Tavecchia G, Olmastroni S, Pezzo F, Focardi S (2009) Nonlinear effects 2362 of winter sea ice on survival probabilities of Adélie penguins. Oecologia 161: 2363 253-265. 2364

Barbraud, C., and H. Weimerskirch. 2001. Emperor penguins and climate change. 2365 Nature 411:183-186. 2366

Barbraud, C., H. Weimerskirch, C. Guinet, and P. Jouventin. 2000. Effect of sea-ice 2367 extent on adult survival of an Antarctic top predator: The snow petrel 2368 Pagodroma nivea. Oecologia (Berlin) 125:483-488. 2369

Barbraud, C., H. Weimerskirch, 2006. Antarctic birds breed later in response to 2370 climate change. Proceedings of the National Academy of Sciences of the 2371 United States of America 103:6248-6251. 2372

Barbraud, C., H. Weimerskirch, 2005. Environmental conditions and breeding 2373 experience affect costs of reproduction in blue petrels. Ecology 86:682-692. 2374

Barnes, D.K.A. and Peck, L.S., 2008. Vulnerability of Antarctic shelf biodiversity to 2375 predicted regional warming. Climate research 37: 149-163. 2376

Bellerby R. G. J. , Schulz K. G. , Riebesell U. , Neill C. , Nondal G. , Heegaard E. , 2377 Johannessen T. , and Brown K. R., 2008. Marine ecosystem community 2378 carbon and nutrient uptake stoichiometry under varying ocean acidification 2379 during the PeECE III experiment Biogeosciences, 5, 1517-1527 2380

Bindoff, N. L., and T. J. McDougall. 2000. Decadal changes along an Indian ocean 2381 section at 32°S and their interpretation. Journal of Physical Oceanography 2382 30:1207-1222. 2383


69

Bindoff, N. L., J. Willebrand, V. Artale, A. Cazanave, J. Gregory, S. Gulev, K. 2384 Hanawa et al. 2007. Observations: Oceanic climate change and sea level. 2385 Contribution of Working Group I to the Fourth Assessment Report of the 2386 Intergovernmental Panel on Climate Change, in D. Q. S. Solomon, M. 2387 Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller, ed. 2388 Climate Change 2007: The Physical Science Basis. Cambridge, U.K., and 2389 New York, U.S.A., Cambridge University Press,. 2390

Bindoff, N.L. and McDougall, T.J., 2000. Decadal changes along an Indian ocean 2391 section at 32°S and their interpretation. Journal of Physical Oceanography, 30: 2392 1207-1222. 2393

Bindoff, N.L. et al., 2007. Observations: Oceanic climate change and sea level. 2394 Contribution of Working Group I to the Fourth Assessment Report of the 2395 Intergovernmental Panel on Climate Change,. In: D.Q. S. Solomon, M. 2396 Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller 2397 (Editor), Climate Change 2007: The Physical Science Basis. Cambridge 2398 University Press,, Cambridge, U.K., and New York, U.S.A. 2399

Biuw, M., L. Boehme, C. Guinet, M. Hindell, D. Costa, J. B. Charrassin, F. Roquet, 2400 F. Bailleul, M. Meredith, S. Thorpe, Y. Tremblay, B. McDonald, Y. H. Park, 2401 S. R. Rintoul, N. Bindoff, M. Goebel, D. Crocker, P. Lovell, J. Nicholson, F. 2402 Monks, and M. A. Fedak. 2007. Variations in behavior and condition of a 2403 Southern Ocean top predator in relation to in situ oceanographic conditions. 2404 Proceedings of the National Academy of Sciences of the United States of 2405 America 104:13705-13710. 2406

Blain S., Quéguiner, B., Armand, L., Belviso, S., Bombled, B., Bopp, L., Bowie, A., 2407 Brunet Blain S., Quéguiner, B., Armand, L., Belviso, S., Bombled, B., Bopp, 2408 L., Bowie, A., Brunet C., Brussaard C., Carlotti, F., Christaki, U., Corbière A., 2409 Durand I., Ebersbach F., Fuda J.L., Garcia N., Gerringa L., Griffiths B., 2410 Guigue C., Guillerm C., Jacquet S., Jeandel C., Laan P., Lefèvre D., Lo 2411 Monaco C., Malits A., Mosseri J., Obernosterer I., Park Y.H., Picheral M., 2412 Pondaven P., Remenyi T., Sandroni V., Sarthou G., Savoye N., Scouarnec L., 2413 Souhaut M., Thuiller D., Timmermans K., Trull T., Uitz J., van Beek P., 2414 Veldhuis M., Vincent D., Viollier E., Vong L. and Wagener T. 2007. Effect of 2415 natural iron fertilization on carbon sequestration in the Southern Ocean. 2416 Nature 446: 26 April 2007, doi:10.1038/nature05700. 2417

Block, BA; Costa, DP; Boehlert, GW, et al., 2002. Revealing pelagic habitat use: the 2418 tagging of Pacific pelagics program. Oceanologica Acta, 25, 255-266. 2419

Boehme, L., M. P. Meredith, S. E. Thorpe, M. Biuw and M. Fedak, 2008: The ACC 2420 frontal system in the South Atlantic: monitoring using merged Argo and 2421 animal-borne sensor data., Journal of Geophysical Research, 113, C09012, 2422 doi:10.1029/2007JC004647. 2423

Boehme, L., M. P. Meredith, S. E. Thorpe, M. Biuw and M. Fedak, 2008: The ACC 2424 frontal system in the South Atlantic: monitoring using merged Argo and 2425 animal-borne sensor data., Journal of Geophysical Research, 113, C09012, 2426 doi:10.1029/2007JC004647. 2427

Böning, C. W., A. Dispert, M. Visbeck, S. R. Rintoul, and F. Schwarzkopf, 2008. 2428 The response of the Antarctic Circumpolar Current to recent climate change, 2429 Nature Geoscience, in press. 2430

Boyer, T.P., J.I. Antonov, S. Levitus, and R. Locarnini, 2005: Linear trends of salinity 2431 for the world ocean, 1955-1998. Geophys. Res. Lett., 32, L01604, 2432 doi:1029/2004GL021791. 2433


70

Bracegirdle, T.J., Connolley, W.M. and Turner, J., 2008. Antarctic climate change 2434 over the twenty first century. Journal of Geophysical Research, 113(D03103): 2435 10.1029/2007JD008933. 2436

Brandt, A.; De Broyer, C.; Gooday, A. J.; Hilbig, B. & Thomson, M. R. A. (2004). 2437 Introduction to ANDEEP (ANtarctic Benthic DEEP-sea biodiversity: 2438 colonization history and recent community patterns) – a tribute to Howard L. 2439 Sanders. Deep-Sea Research II, 51: 1457-1465. 2440

Brandt, A.; Gooday, A.J.; Brandão, S.; Brix, S.; Brökeland, W.; Cdhagen, T.; 2441 Choudhury, M.; Cornelius, N.; Danis, B.; De Mesel, I.; Diaz, R.J.; Gillan, 2442 D.C.; Ebbe, B.; Howe, J.A.; Janussen, D.; Kaiser, S.; Linse, K.; Malyutina, 2443 M.; Pawlowski, J.; Raupach, M. & Vanreusel, A. 2007. First insights into the 2444 biodiversity and biogeography of the Southern Ocean deep sea. Nature 447: 2445 307-311. 2446

Broecker, W.S. 1997. Thermohaline circulation the Achilles heel of our climate 2447 system: Will man-made CO2 upset the current balance? Science 278:1582-2448 1588. 2449

Burns, J. M., D. P. Costa, M. A. Fedak, M. A. Hindell, C. J. A. Bradshaw, N. J. Gales, 2450 B. McDonald, S. J. Trumble, and D. E. Crocker. 2004. Winter habitat use and 2451 foraging behavior of crabeater seals along the Western Antarctic Peninsula. 2452 Deep Sea Research Part II: Topical Studies in Oceanography 51:2279-2303. 2453

Burns, J. M., M. A. Hindell, C. J. A. Bradshaw, and D. P. Costa. 2008. Fine-scale 2454 habitat selection of crabeater seals as determined by diving behavior. Deep 2455 Sea Research Part II: Topical Studies in Oceanography 55:500-514. 2456

Butler, A. H., D. W. J. Thompson, and K. R. Gurney (2007), Observed relationships 2457 between the Southern Annular Mode and atmospheric carbon dioxide, Global 2458 Biogeochem. Cycles, 21, GB4014, doi:10.1029/2006GB002796. 2459

Charrassin, J. B., M. Hindell, S. R. Rintoul, F. Roquet, S. Sokolov, M. Biuw, D. 2460 Costa, L. Boehme, P. Lovell, R. Coleman, R. Timmermann, A. Meijers, M. 2461 Meredith, Y. H. Park, F. Bailleul, M. Goebel, Y. Tremblay, C. A. Bost, C. R. 2462 McMahon, I. C. Field, M. A. Fedak, and C. Guinet. 2008. Southern Ocean 2463 frontal structure and sea-ice formation rates revealed by elephant seals. 2464 Proceedings of the National Academy of Sciences 105:11634-11639 %R 2465 11610.11073/pnas.0800790105. 2466

Clark, P.U., Pisias, N.G., Stocker, T.F. and Weaver, A.J. 2002. The role of the 2467 thermohaline circulation in abrupt climate change. Nature 415:863-869. 2468

Clarke, A. & Johnston, N.M. (2003). Antarctic marine benthic diversity. Oceanogr. 2469 Mar. Biol., 41: 47-114. 2470

Clarke, A., 2003. Costs and consequences of evolutionary temperature adaptation. 2471 Trends in Ecology and Evolution 18, 573-581. 2472

Clarke, A., Murphy, E.J., Meredith, M.P., King, J.C., Peck, L.S., Barnes, D.K.A., and 2473 Smith, R.C., 2007. Climate change and the marine ecosystem of the western 2474 Antarctic Peninsula. Philosophical Transactions of the Royal Society B, 2475 362:149-166 2476

Clarke, A.; Meredith, M. P.; Wallace, M. I.; Brandon, M. A. & Thomas, D. N. 2008. 2477 Seasonal and interannual variability in temperature, chlorophyll and 2478 macronutrients in northern Marguerite Bay, Antarctica. Deep-Sea Research, 2479 Part II, 55, 18-19, 1988-2006. 2480

Comiso, J. C., and F. Nishio (2008), Trends in the sea ice cover using enhanced and 2481 compatible AMSR-E, SSM/I, and SMMR data, J. Geophys. Res., 113, 2482 C02S07, doi:10.1029/2007JC004257. 2483


71

Constable, A.J., Doust, S. (2009) Southern Ocean Sentinel - an international program 2484 to assess climate change impacts on marine ecosystems: report of an 2485 international Workshop, Hobart, April 2009. ACE CRC, Commonwealth of 2486 Australia, and WWF-Australia. 2487

Costa DP, Croxall JP, Duck CD (1989) Foraging energetics of Antarctic fur seals in 2488 relation to changes in prey availability. Ecology 70:596-606. 2489

Costa, D. P. 2007. A conceptual model of the variation in parental attendance in 2490 response to environmental fluctuation: foraging energetics of lactating sea 2491 lions and fur seals. Aquatic Conservation: Marine and Freshwater Ecosystems 2492 17:S44-S52. 2493

Costa, D. P., J. M. Klinck, E. E. Hofmann, M. S. Dinniman, and J. M. Burns. 2008. 2494 Upper ocean variability in West Antarctic Peninsula continental shelf waters 2495 as measured using instrumented seals. Deep Sea Research Part II: Topical 2496 Studies in Oceanography 55:323-337. 2497

Croxall JP (1992) Southern Ocean environmental changes - effects on seabird, seal 2498 and whale populations. Philosophical Transactions of the Royal Society of 2499 London Series B-Biological Sciences 338:319-328. 2500

Croxall JP, Trathan PN, Murphy EJ (2002) Environmental change and Antarctic 2501 seabird populations. Science 297:1510-1514. 2502

Cubillos, J.C., Wright, S. W., Nash, G., de Salas, M. F., Griffiths, B., Tilbrook, B., 2503 Poisson, A., and Hallegraeff, G. M. (2007) Calcification morphotypes of the 2504 coccolithophorid Emiliania huxleyi in the Southern Ocean: changes in 2001 to 2505 2006 compared to historical data. Marine Ecology Progress Series 348, 47-54 2506

Curran, M. A. J., van Ommen, T. D., Morgan, V. I., Phillips, K. L. and Palmer, A. S., 2507 2003. Ice core evidence for sea ice decline since the 1950s, Science, 302, 2508 1203-1206. 2509

Curry, R., B. Dickson, and I. Yashayaev. 2003. A change in the freshwater balance of 2510 the Atlantic Ocean over the past four decades. Nature 426:826–829. 2511

de la Mare, W. K., 1997. Abrupt mid-twentieth-century decline in Antarctic sea ice 2512 extent from whaling records, Nature, 389, 57-60. 2513

Dickson, B., I. Yashayaev, J. Meincke, B. Turrell, S. Dye and J. Holfort (2002), Rapid 2514 freshening of the deep North Atlantic Ocean over the past four decades. 2515 Nature, 416, 832-837. 2516

Drinkwater, MR; Liu, X; Harms, S, 2001. Combined satellite- and ULS-derived sea-2517 ice flux in the Weddell Sea, Antarctica. Annals of Glaciology, 33, 125-132. 2518

Ducklow, H. W., K. Baker, D. G. Martinson, L. B. Quetin, R. M. Ross, R. C. Smith, 2519 S. E. Stammerjohn et al. 2007. Marine pelagic ecosystems: the West Antarctic 2520 Peninsula. Philosophical Transactions of the Royal Society B: Biological 2521 Sciences 362:67-94. 2522

Ducklow, H.W., 2008. Long-term studies of the marine ecosystem along the west 2523 Antarctic Peninsula. Deep Sea Research Part II: Topical Studies in 2524 Oceanography, Volume 55, Issues 18-19, , Pages 1945-1948 2525

Durack, P.J and S.E. Wijffels, 2010. Fifty-Year Trends in Global Ocean Salinities 2526 and their relationship to Broad-Scale Warming. Journal of Climate. 2527

Emmerson, L.M., and Southwell, C. (2008). Sea-ice cover and its influence on Adélie 2528 penguin reproductive performance. Ecology 89: 2096-2102 2529

Enzenbacher, D.J. 1992. Antarctic tourism and environmental concerns. Marine 2530 Pollution Bulletin 25:9-12. 2531


72

Fahrbach, E., Hoppema, M., Rohardt, G., Schröder, M. and Wisotzki, A., 2004. 2532 Decadal-scale variations of water mass properties in the deep Weddell Sea. 2533 Ocean Dynamics, 54(77-91). 2534

Fahrbach, E., M. Hoppema, G. Rohardt, M. Schröder, and A. Wisotzki. 2004. 2535 Decadal-scale variations of water mass properties in the deep Weddell Sea. 2536 Ocean Dynamics 54. 2537

Feely, R.A., V. J. Fabry, A. G. Dickson, J.-P. Gattuso, J. Bijma, U. Riebesell, S. 2538 Doney, C. Turley, T. Saino, K. Lee, K. Anthony, J. Kleypas, 2010. An 2539 international observational network for ocean acidification. In: Proceedings 2540 of OceanObs’09: Sustained Ocean Observations and Information for Society 2541 (Vol. 2), Venice, Italy, 21-25 September 2009, Hall, J., Harrison D.E. & 2542 Stammer, D., Eds., ESA Publication WPP-306, in press. 2543

Forcada J, Trathan PN, Reid K, Murphy EJ (2005) The effects of global climate 2544 variability in pup production of Antarctic fur seals. Ecology 86:2408-2417. 2545

Fraser, W.R. and Hofmann, E.E. 2003. A predator’s perspective on causal links 2546 between climate change, physical forcing and ecosystem response. Marine 2547 Ecology Progress Series 265:1-15. 2548

Fraser, W.R. and Patterson, D.L. 1997. Human disturbance and long-term changes in 2549 Adélie penguin populations: a natural experiment at Palmer Station, Antarctic 2550 Peninsula. Antarctic Communities: species, Structure and Survival, 445-446 2551 pp. 2552

Fraser, W.R., Trivelpiece, W.Z., Ainley, D.G. and Trivelpiece, S.G. 1992. Increases 2553 in Antarctic penguin populations-reduced competiion with whales or a loss of 2554 sea ice due to environmental warming. Polar Biology 11:525-532. 2555

Frenot, Y., Chown, S.L., Whinam, J. Selkirk, P.M., Convey, P. Skotnicki, M. and 2556 Bergstrom, D.M. 2005. Biological invations in the Antarctic: extent, impacts 2557 and implications. Biological Reviews 80:45-72. 2558

Fuda J.L., Garcia N., Gerringa L., Griffiths B., Guigue C., Guillerm C., Jacquet S., 2559 Fyfe, J. C. 2006. Southern Ocean Warming Due to Human Influence. 2560 Geophysical Research Letters 33:10.1029/2006GL027247. 2561

Fyfe, J.C., 2006. Southern Ocean Warming Due to Human Influence. Geophysical 2562 Research Letters, 33(L19701): 10.1029/2006GL027247. 2563

Fyfe, J.C., Saenko, O.A., Zickfield, K., Eby, M. and Weaver, A., 2007. The role of 2564 poleward intensifying winds on Southern Ocean warming. Journal of Climate, 2565 20(5391-5400). 2566

Fyfe, J. C., G. J. Boer, and G. M. Flato (1999), The Arctic and Antarctic oscillations 2567 and their projected changes under global warming, Geophys. Res. Lett., 2568 26(11), 1601–1604, doi:10.1029/1999GL900317. 2569

Gent, P. R. and J. C. McWilliams, 1990. : Isopycnal mixing in ocean circulation 2570 models. Journal of Physical Oceanography, 20, 150-155. 2571

Gille, S.T., 2002. Warming of the Southern Ocean Since the 1950s. Science, 295: 2572 1275-1277. 2573

Gille, S.T., 2008. Decadal-scale temperature trends in the Southern Hemisphere 2574 ocean. Journal of Climate, 21, 4749-4765. 2575

Goodwin, ID; van Ommen, TD; Curran, MAJ, et al., 2004. Mid latitude winter 2576 climate variability in the South Indian and southwest Pacific regions since 2577 1300 AD. Climate Dynamics, 22, 783-794. 2578

Gordon, A. L., 1991. 2 stable modes of Southern Ocean stratification. In: Deep 2579 Convection and Deep Water Formation in the Oceans, 57, 17-35. 2580


73

Grant S, Constable A, Raymond B, Doust S. 2006. Bioregionalisation of the Southern 2581 Ocean: Report of Experts Workshop, WWF- Australia and ACE CRC, Hobart, 2582 September 2006. pp. 2583

Gregory, J.M., P.A. Stott, D.J. Cresswell, N.A. Rayner, C. Gordon, D.M.H. Sexton, 2584 Recent and future changes in Arctic sea ice simulated by the HadCM3 2585 AOGCM, 2002. Geophys. Res. Lett., 29 (24), 2175, 2586 doi:10.1029/2001GL014575 2587

Gutt J, Piepenburg D (2003) Scale-dependent impact on diversity of Antarctic benthos 2588 caused by grounding of icebergs. Marine Ecology Progress Series 253: 77-83. 2589

Gutt, J. 2007. Antarctic macro-zoobenthic communities: a review and an ecological 2590 classification, Antarctic science, 19(2): 165-182, 2591 doi:10.1017/S0954102007000247. 2592

Gutt, J.; Koubbi, P. & Eléaume, M. 2007. Mega-epibenthic diversity off Terre Adélie 2593 (Antarctica) in relation to disturbance. Polar Biology, 30(10): 1323-1329, 2594 doi:10.1007/s00300-007-0293-z. 2595

Hall, A. and M. Visbeck, 2002. Synchronous variability in the Southern Hemisphere 2596 atmosphere, sea ice and ocean resulting from the annular mode. J. Climate, 2597 15, 3043-3057. 2598

Hallberg, R. and A. Gnanadesikan, 2006. The role of eddies in determining the 2599 structure and response of the wind-driven southern hemisphere overturning: 2600 Results from the Modeling Eddies in the Southern Ocean (MESO) project. 2601 JOURNAL OF PHYSICAL OCEANOGRAPHY Volume: 36 Issue: 12 2602 Pages: 2232-2252. 2603

Handegard, N. O., D. Demer, R. Kloser, P. Lehodey, O. Maury, Y. Simard, 2010. 2604 Toward a global ocean ecosystem Mid-trophic Automatic Acoustic Sampler 2605 (MAAS). Proceedings of OceanObs’09: Sustained Ocean Observations and 2606 Information for Society (Vol. 2), Venice, Italy, 21-25 September 2009, Hall, 2607 J., Harrison D.E. & Stammer, D., Eds., ESA Publication WPP-306, in press. 2608

Hellmer and Timmerman, 2004 2609 Hofmann EE, Wiebe PH, Costa DP, Torres JJ (2004) An overview of the Southern 2610

Ocean Global Ocean Ecosystems Dynamics Program, Deep-Sea Research II, 2611 51:1921-1924. 2612

Hofmann EE, Wiebe PH, Costa DP, Torres JJ (2008) Introduction to dynamics of 2613 plankton, krill, and predators in relation to environmental features of the 2614 western Antarctic Peninsula and related areas: SO GLOBEC Part II, Deep-Sea 2615 Research II, 55:269-270. 2616

Hogg, A.M., Meredith, M.P., Blundell, J.R. and Wilson, C., 2008. Eddy Heat Flux in 2617 the Southern Ocean: Response to Variable Wind Forcing. Journal of Climate, 2618 21(4): 608-620. 2619

Holm–Hansen O., Kahru M., Hewes C.D., Kawaguchi S., Kameda T., Sushin V.A., 2620 Krasovski, 2004a. Factors influencing the distribution, biomass, and 2621 productivity of phytoplankton in the Scotia Sea and adjoining waters. Deep–2622 Sea Research Part II— Topical Studies in Oceanography 51: 1333–1350. 2623

Holm–Hansen O., Naganobu M., Kawaguchi S., Kameda T., Krasovski I., 2624 Tchernyshkov P., I., Priddle J., Korb R., Hewitt R.P. and Mitchell, B.G. 2625 2004b. Temporal and spatial Holm–Hansen O., Kahru M., Hewes C.D., 2626 Kawaguchi S., Kameda T., Sushin V.A., Krasovski I., Priddle J., Korb R., 2627 Hewitt R.P. and Mitchell, B.G. 2004b. Temporal and spatial distribution of 2628 chlorophyll–a in surface waters of the Scotia Sea as determined by both 2629


74

shipboard measurements and satellite data. Deep–Sea Research Part II—2630 TopicalStudies in Oceanography 51: 1323–1331. 2631

Hood., E. M. and Co-Authors -Sloyan, B. M. (2009). Ship-based repeat hydrography: 2632 a strategy for a sustained global survey. In Proceedings of OceanObs’09: 2633 Sustained Ocean Observations and Information for Society (vol. 2), Venice, 2634 Italy, 21-25 September 2009, Hall, J., Harrison, D. E., and Stammer, D., Eds., 2635 ESA publication WPP-306 2636

Hosie, G.W., Fukuchi, M. and Kawaguchi, S. (2003) Development of the Southern 2637 Ocean Continuous Plankton Recorder Survey. Progress in Oceanography 58 2638 (2-4), 263-283 2639

Hughes, C.W., Woodworth, P.L., Meredith, M.P., Stepanov, V., Whitworth, T. and 2640 Pyne A.R. 2003. Coherence of Antarctic sea levels, Southern Hemisphere 2641 Annular Mode, and flow through Drake Passage. Geophysical Research 2642 Letters, 30(9), 1464, doi:10.1029/2003GL017240. 2643

Hunt, B. P. V.1, Pakhomov, E. A., Hosie, G. W., Siegel, V., Ward, P. Bernard, K. 2644 (2008) Pteropods in Southern Ocean ecosystems. Progress in Oceanography. 2645 78, 193-221 2646

IMBER (2005) Science Plan and Implementation Strategy. IGBP Report No. 52, 2647 Stockholm. 2648

IPCC (2007) Climate change 2007: Synthesis report. Summary for Policy makers., 2649 Intergovernmental Panel On Climate Change. 2650

Ivchenko, VO; Zalesny, VB; Drinkwater, MR, 2004. Can the equatorial ocean 2651 quickly respond to Antarctic sea ice/salinity anomalies? GEOPHYSICAL 2652 RESEARCH LETTERS Volume: 31 Issue: 15 Article Number: L15310. 2653

Jacobs, S. S. (2006). Observations of change in the Southern Ocean. Phil. Trans. 2654 Roy. Soc. A, 364, 1657-1681, doi:10.1098/rsta.2006.1794. 2655

Jacobs, S. S., C. F. Giulivi, and P. A. Mele. 2002. Freshening of the Ross Sea during 2656 the late 20th century. Science 297:386-389. 2657

Jacobs, S.S. (2004). Bottom water production and its links with the thermohaline 2658 circulation. Antarctic Science 16 (4): 427-437. 2659

Jacobs, S. J. and C. F. Giulivi, 2010. Large Multi-decadal Salinity Trends near the 2660 Pacific-Antarctic Continental Margin. Journal of Climate, 2661 10.1175/2010JCLI3284.1 2662

Jenkins, A; Dutrieux, P; Jacobs, SS, et al., 2010. Observations beneath Pine Island 2663 Glacier in West Antarctica and implications for its retreat. Nature Geoscience, 2664 3, 468-472. 2665

Jenouvrier, S., C. Barbraud, and H. Weimerskirch. 2003. Effects of climate variability 2666 on the temporal population dynamics of southern fulmars. Journal of Animal 2667 Ecology 72:576-587. 2668

Jenouvrier, S.. 2005. Long-term contrasted responses to climate of two Antarctic 2669 seabird species. Ecology 86:2889-2903. 2670

Jenouvrier, S., C. Barbraud, and H. Weimerskirch. 2006. Sea ice affects the 2671 population dynamics of Adélie penguins in Terre Adélie. Polar Biology 2672 29:413-423. 2673

Johannessen et al., 2001 2674 Johnson, G.C. and Doney, S.C., 2006. Recent western South Atlantic bottom water 2675

warming. Geophysical Research Letters, 33(L14614): 2676 10.1029/2006GL026769. 2677

King, J. C., J. Turner, G. J. Marshall, W. M. Connolley, and T. A. Lachlan-Cope. 2678 2004. Antarctic Peninsula Climate Variability And Its Causes As Revealed By 2679


75

Analysis Of Instrumental Records, Pages 17-30 in E. Domack, A. Burnett, P. 2680 Convey, M. Kirby, and R. Bindschadler, eds. Antarctic Peninsula Climate 2681 Variability: A historical and Paleoenvironmental Perspective. Antarctic 2682 Research Series. Washington, DC, American Geophysical Union. 2683

Korb R.E. and Whitehouse M. 2004. Contrasting primary production regimes around 2684 South Georgia, Southern Ocean: large blooms versus high nutrient, low 2685 chlorophyll waters. Deep–Sea Research Part I—Oceanographic Research 2686 Papers 51: 721–738. 2687

Korb R.E., Whitehouse M.J., Thorpe S.E. and Gordon M. 2005. Primary production 2688 across the Scotia Sea in relation to the physico–chemical environment. Journal 2689 of Marine Systems 57: 231–249. 2690

Laws, R. M., A. Baird, and M. M. Bryden. 2003a. Breeding season and embryonic 2691 diapause in crabeater seals (Lobodon carcinophagus). Reproduction 2692 (Cambridge) 126:365-370. 2693

Laws, R. M., 2003b. Size and growth of the crabeater seal Lobodon carcinophagus 2694 (Mammalia: Carnivora). Journal of Zoology (London) 259:103-108. 2695

Laws, R.M. 1985. The ecology of the Southern Ocean. American Scientist, 73:26-40. 2696 Le Quéré, C. Christian Rödenbeck, Erik T. Buitenhuis, Thomas J. Conway, Ray 2697

Langenfelds, Antony Gomez, Casper Labuschagne, Michel Ramonet, 2698 TakakiyoNakazawa, Nicolas Metzl, Nathan Gillett, Martin Heimann (2007) 2699 Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change 2700 .Science 22 June 2007: Vol. 316. no. 5832, pp. 1735 – 1738, DOI: 2701 10.1126/science.1136188 2702

Le Traon, PY; Dibarboure, G; Ducet, N, 2001. Use of a high-resolution model to 2703 analyze the mapping capabilities of multiple-altimeter missions. J. Atmos. 2704 Ocean. Tech., 18, 1277-1288. 2705

Leaper R, Cooke J, Trathan P, Reid K, Rowntree V, Payne R (2006) Global climate 2706 drives southern right whale (Eubalaena australis) population dynamics. 2707 Biology Letters 2:289-292. 2708

Lenton, A., and R. J. Matear (2007), Role of the Southern Annular Mode (SAM) in 2709 Southern Ocean CO2 uptake, Global Biogeochem. Cycles, 21, GB2016, 2710 doi:10.1029/2006GB002714. 2711

Levitus, S., Antonov, J. and Boyer, T., 2005. Warming of the world ocean, 1955–2712 2003. Geophysical Research Letters, 32(2): 10.1029/2004GL021592. 2713

Loeb, V., V. Siegel, O. Holm-Hansen, R. Hewitt, W. Fraser, W. Trivelpiece & S. 2714 Trivelpiece. 1997. Effects of sea-ice extent and krill or salp dominance on the 2715 Antarctic food web, Nature, 386:897-900. 2716

Lovenduski, N. S., N. Gruber, S. C. Doney, and I. D. Lima (2007), Enhanced CO2 2717 outgassing in the Southern Ocean from a positive phase of the Southern 2718 Annular Mode, Global Biogeochem. Cycles, 21, GB2026, 2719 doi:10.1029/2006GB002900. 2720

Lubin, D. and R. A. Massom, 2006. Polar remote sensing, Vol 1, Atmosphere and 2721 oceans, Praxis Publishing Ltd, Chichester, UK, 756 pp. 2722

Lumpkin, R and Speer, K, 2007. Global ocean meridional overturning. JOURNAL 2723 OF PHYSICAL OCEANOGRAPHY Volume: 37 Pages: 2550-2562. 2724

Marchant, H.J., Davidson, A.T. and Wright, S.W. (1987) The distribution and 2725 abundance of chroococoid cyanobacteria in the Southern Ocean. Proc. NIPR 2726 Symp. Polar Biol. 1, 1-19. 2727

Marshall, G.J., 2003. Trends in the Southern Annular Mode from Observations and 2728 Reanalyses. Journal of Climate, 16: 4134-4143. 2729


76

Marshall, J. and T. Radko: 2003, Residual mean solutions for the Antarctic 2730 Circumpolar Current and its associated thermohaline circulation. J. Phys. 2731 Oceanogr., 33, 2341–2354. 2732

Masuda, S., T. Awaji, N. Sugiura, J.P. Mathews, T. Toyoda, Y. Kawai, T. Doi, S. 2733 Kouketsu, H. Igarashi, K. Katsumata, H. Uchida, T. Kawano, and M. 2734 Fukasawa, 2010. Simulated rapid warming of abyssal North Pacific waters. 2735 Science. 2736

Mayewski, PA; Meredith, MP; Summerhayes, CP, et al., 2009. State of the Antarctic 2737 and Southern Ocean Climate System. Rev. of Geophys., 47, Article Number: 2738 RG1003. 2739

McClintock, J., H. Ducklow, and W. Fraser. 2008. Ecological Responses to Climate 2740 Change on the Antarctic Peninsula. American Scientist 96:302-310. 2741

McConnell, B. J. and M. A. Fedak. 1996. Movements of southern elephant seals. 2742 Canadian Journal of Zoology 74:1485-1496. 2743

McDonald, B. I., D. E. Crocker, J. M. Burns, and D. P. Costa. 2008. Body condition 2744 as an index of winter foraging success in crabeater seals (Lobodon 2745 carcinophaga). Deep-Sea Research Part Ii-Topical Studies in Oceanography 2746 55:515-522. 2747

McMahon, C. R., L. C. Field, C. J. A. Bradshaw, G. C. White, and M. A. Hindell. 2748 2008. Tracking and data-logging devices attached to elephant seals do not 2749 affect individual mass gain or survival. Journal of Experimental Marine 2750 Biology and Ecology 360:71-77. 2751

McNeil, BI; Matear, RJ , 2008. Southern Ocean acidification: A tipping point at 450-2752 ppm atmospheric CO2, PROCEEDINGS OF THE NATIONAL ACADEMY 2753 OF SCIENCES OF THE UNITED STATES OF AMERICA Volume: 105 2754 Issue: 48 Pages: 18860-18864. 2755

Meredith, M P., Renfrew, I. A., Boehme, L., Biuw, M., Fedak, M. A; 2009 (in Press) 2756 "Seasonal evolution of the upper-ocean adjacent to the South Orkney Islands, 2757 Southern Ocean: results from a “lazy biological mooring” Deep Sea 2758 Research Part II 2759

Meredith, M. P., and A. M. Hogg. 2006. Circumpolar response of Southern Ocean 2760 eddy activity to changes in the Southern Annular Mode. Geophysical Research 2761 Letters 33(16):10.1029/2006GL026499. 2762

Meredith, M. P., and J. C. King. 2005. Rapid climate change in the ocean to the west 2763 of the Antarctic Penisula during the second half of the twentieth century. 2764 Geophysical Research Letters 32:10.1029/2005GL024042. 2765

Meredith, M.P. and King, J.C., 2005. Rapid climate change in the ocean to the west of 2766 the Antarctic Penisula during the second half of the twentieth century. 2767 Geophysical Research Letters, 32(L19604): 10.1029/2005GL024042. 2768

Meredith, M.P., Garabato, A.C.N., Gordon, A.L. and Johnson, G.C., 2008. Evolution 2769 of the Deep and Bottom Waters of the Scotia Sea, Southern Ocean, 1995-2770 2005. Journal of Climate, 21(13): 3327-3343. 2771

Meredith, M.P., P.L. Woodworth, C.W. Hughes and V. Stepanov, 2004. Changes in 2772 the ocean transport through Drake Passage during the 1980s and 1990s, forced 2773 by changes in the Southern Annular Mode. Geophysical Research Letters, 2774 31(21), L21305, 10.1029/2004GL021169 2775

Metzl, N., 2009. Decadal increase of oceanic carbon dioxide in Southern Indian 2776 Ocean surface waters (1991-2007). Deep-Sea Research II, 56, 607-619. 2777


77

Millif, R. F., Morzel, J., Danabasoglu, G. & Chin, T. M. (2001). Ocean general 2778 circulation model sensitivity to forcing from scatterometer winds, J. Geophys. 2779 Res. 104C: 11337–11358. 2780

Mitchum et al. 2001 2781 Mohana, R., Mergulhaoc, L.P., Gupthad, M.V.S., Rajakumarb, A., Thambana, M., 2782

AnilKumara, N., Sudhakara, M. and Ravindraa, R. (2008) Ecology of 2783 coccolithophores in the Indian sector of the Southern Ocean. Marine 2784 Micropaleontology 67, 30-45 2785

Moisan, JR and PP Niiler, 1998. The seasonal heat budget of the North Pacific: Net 2786 heat flux and heat storage rates (1950-1990). J. Phys. Oceanog., 28, 401-421. 2787

Montes-Hugo, M., S. C. Doney, H. W. Ducklow, W. Fraser, D. Martinson, S. E. 2788 Stammerjohn, and O. Schofield. 2009. Recent Changes in Phytoplankton 2789 Communities Associated with Rapid Regional Climate Change Along the 2790 Western Antarctic Peninsula. Science 323:1470-1473. 2791

Montone and Webber 2792 Moy, A.D., Howard, W.R., Bray, S.G. & Trull T.W., 2009. Reduced calcification in 2793

modern Southern Ocean planktonic foraminifera. Nature Geoscience 2794 doi:10.1038/ngeo460. 2795

Murphy EJ, Trathan PN, Watkins JL, Reid K, Meredith MP, Forcada J, Thorpe SE, 2796 Johnston NM, Rothery P (2007a) Climatically driven fluctuations in Southern 2797 Ocean ecosystems. Proceedings of the Royal Society B-Biological Sciences 2798 274:3057-3067. 2799

Murphy, E.J., Watkins, J.L., Trathan, P.N. Reid, K. Meredith, M.P., Thorpe, S.E., 2800 Johnston, N.M., Clarke, A., Tarling, G.A., Collins, M.a., Forcada, J., Sreeve, 2801 R.S., Atkinson, A., Korb, R., Whitehouse, M.J., Ward, P., Rodhouse, P.G., 2802 Enderlein, P., Hirst, A.G., Martin, A.R., Hill, S.L., Staniland, I.J., Pond, D.W., 2803 Briggs, D.R., Cunningham, N.J., and Fleming, A.H. 2007. Spatial and 2804 temporal operation of the Scotia Sea ecosystem: a review of large-scale links 2805 in a krill centered food web. Proceedings Royal Society B, 362:113-148. 2806

Garabato, A. C. N., L. Jullion, D. P. Stevens, K. J. Heywood, and B. A. King. 2009. 2807 Variability of Subantarctic Mode Water and Antarctic Intermediate Water in 2808 Drake Passage during the Late 20th and Early 21st Centuries. Journal of 2809 Climate, 22, 3661-3688. 2810

Garabato, ACN; Polzin, KL; King, BA, et al., 2004. Widespread intense turbulent 2811 mixing in the Southern Ocean. Science, 303, 210-213. 2812

Nicholls K. W., L. Boehme, M. Biuw and M. A. Fedak, 2008: Wintertime ocean 2813 conditions over the southern Weddell Sea continental shelf, Antarctica. 2814 Geophys. Res. Lett., 35, L21605 2815

Nicholls, K.W., and A. Jenkins, 1993. Temperature and Salinity beneath Ronne Ice 2816 Shelf, Antarctica, Journal of Geophysical Research, 98, 22553-22568, 1993. 2817

Nicholls, K.W., and K. Makinson, Ocean circulation beneath the western Ronne 2818 IceShelf, as derived from in situ measurements of water currents and 2819 properties, in Ocean, Ice, and Atmosphere: Interactions at the Antarctic 2820 Continental Margin, edited by S.S. Jacobs, and R.F. Weiss, pp. 301-318, 2821 AGU, Washington D.C.,1998. 2822

Nicol, S., J. Clarke, S. J. Romaine, S. Kawaguchi, G. Williams, and G. W. Hosie. 2823 2008. Krill (Euphausia superba) abundance and Adélie penguin (Pygoscelis 2824 adeliae) breeding performance in the waters off the Bechervaise Island colony, 2825 East Antarctica in 2 years with contrasting ecological conditions. Deep-Sea 2826 Research Part Ii-Topical Studies in Oceanography 55:540-557. 2827


78

Niiler, PP; Maximenko, NA; McWilliams, JC, 2003. Dynamically balanced absolute 2828 sea level of the global ocean derived from near-surface velocity observations. 2829 Geophys. Res. Let., 30, Article Number: 2164. 2830

Olbers, D; Borowski, D; Volker, C, et al., 2004. The dynamical balance, transport 2831 and circulation of the Antarctic Circumpolar Current. Antarctic Science, 16, 2832 439-470. 2833

Orr JC, Fabry VJ, Aumont O, Bopp L, Doney SC, Feely RA, Gnanadesikan A, 2834 Gruber N, Ishida A, Joos F, Key RM, Lindsay K, Maier-Reimer E, Matear R, 2835 Monfray P, Mouchet A, Najjar RG, Plattner GK, Rodgers KB, Sabine CL, 2836 Sarmiento JL, Schlitzer R, Slater RD, Totterdell IJ, Weirig MF, Yamanaka Y, 2837 Yool A (2005) Anthropogenic ocean acidification over the twenty-first 2838 century and its impact on calcifying organisms. Nature 437:681-686. 2839

Orsi, A.H., W. M. Smethie and J. B. Bullister (2002), On the total input of Antarctic 2840 waters to the deep ocean: A preliminary estimate from chlorofluorocarbon 2841 measurements. J. Geophys. Res., 107(C8), 3122. 2842

Orsi, A.H., and T.W. Whitworth III, 2005: Hydrographic Atlas of the World Ocean 2843 Circulation Experiment (WOCE). Volume 1: Southern Ocean. (eds. M. 2844 Sparrow, P. Chapman and J. Gould), International WOCE Project Office, 2845 Southampton, U.K., ISBN 0-904175-49-9. 2846

Parkinson, CL , 2004. Southern Ocean sea ice and its wider linkages: insights 2847 revealed from models and observations. Antarctic Science, 16, 387-400. 2848

Peck, L. S., K. E. Webb, and D. M. Bailey. 2004. Extreme sensitivity of biological 2849 function to temperature in Antarctic marine species. Functional Ecology 2850 18:625-630. 2851

Peck, Lloyd S.; Convey, Peter; Barnes, David K.A.. 2006 Environmental constraints 2852 on life histories in Antarctic ecosystems: tempos, timings and predictability. 2853 Biological Reviews of the Cambridge Philosophical Society, 81 (1). 75-109. 2854 10.1017/S1464793105006871 2855

Priddle J., Korb R., Brandon M., Demer D., Hewitt R.P., Kahru M.and Hewes C.D. 2856 Pritchard, H. & Vaughan, D., 2007. Widespread acceleration of tidewater 2857 glaciers on the Antarctic Peninsula. J. Geophys. Res. 112 2858 (doi:10.1029/2006JF000597). 2859

Pritchard, HD; Vaughan, DG, 2007. Widespread acceleration of tidewater glaciers on 2860 the Antarctic Peninsula. J. Geophys. Res. – Earth Surface, 112, Article 2861 Number: F03S29. 2862

Reid, K. and Croxall, J.P. 2001. Environmental response of upper trophic-level 2863 predators reveals a system change in an Antarctic marine ecosystem. 2864 Proceedings Royal Society B 268:377-384. 2865

Reynolds 2001 2866 Richardson, G., M.R. Wadley, K.J. Heywood, D.P. Stevens and H.T. Banks (2005) 2867

Short-term climate response to a freshwater pulse in the Southern Ocean, 2868 Geophysical Research Letters, 32, L03702, doi: 10.1029/2004GL021586. 2869

Rignot, E. and S. S. Jacobs, (2002), Rapid bottom melting widespread near Antarctic 2870 ice sheet grounding lines. Science 296, 2020-2023. 2871

Rignot, E. et al., 2004. Accelerated ice discharge from the Antarctic Peninsula 2872 following the collapse of Larsen B ice shelf. Geophys. Res. Lett. 31, L18401. 2873

Rignot, E; Bamber, JL; Van Den Broeke, MR, et al., 2008. Recent Antarctic ice mass 2874 loss from radar interferometry and regional climate modelling. NATURE 2875 GEOSCIENCE Volume: 1 Issue: 2 Pages: 106-110. 2876


79

Rintoul, S. R. 2007. Rapid freshening of Antarctic Bottom Water formed in the Indian 2877 and Pacific oceans. Geophysical Research Letters 34:10.1029/2006GL028550. 2878

Rintoul, S. R., C. Hughes and D. Olbers, 2001. The Antarctic Circumpolar System. 2879 In: Ocean Circulation and Climate, G. Siedler, J. Church, and J. Gould, (Eds.), 2880 Academic Press, 271-302. 2881

Rintoul, S. R., J. Church, E. Farhbach, M. Garcia, A. Gordon, B. King, R. Morrow, A. 2882 Orsi, and K. Speer, 2002: Monitoring and understanding Southern Ocean 2883 variability and its impact on climate: A strategy for sustained observations. In: 2884 Observing the Ocean in the 21st Century, C. J. Koblinsky and N. R. Smith 2885 (Eds.), Bureau of Meteorology, Melbourne, Australia, pp. 486-508. 2886

Rooney et al., 2006 2887 Royal Society (2005) Ocean acidification due to increasing atmospheric carbon 2888

dioxide. Policy document 12/05. The Royal Society, London. 60 pp 2889 Sabine, CL; Feely, RA; Gruber, N, et al., 2004. The oceanic sink for anthropogenic 2890

CO2, SCIENCE Volume: 305 Issue: 5682 Pages: 367-371.. 2891 Sarmiento, JL; Gruber, N; Brzezinski, MA, et al., 2004. High-latitude controls of 2892

thermocline nutrients and low latitude biological productivity. NATURE 2893 Volume: 427 Issue: 6969 Pages: 56-60. 2894

Sarmiento, JL; Hughes, TMC; Stouffer, RJ, et al., 1998. Simulated response of the 2895 ocean carbon cycle to anthropogenic climate warming. Nature, 393, 245-249. 2896

Sarukhanian, E. and I. Frolov, 2004. Preparation for the International Polar Year 2897 2007-2008, joint WMO/IOC technical commission for Oceanography and 2898 marine meteorology (JCOMM) Management committee, man-iii/doc. 2899 5.3(2)(5.iii.2004) 2900

Schofield, O; Ducklow, HW; Martinson, DG, et al., 2010. How Do Polar Marine 2901 Ecosystems Respond to Rapid Climate Change?, Science, 328, 1520-1523. 2902

Schuster et al., XXXX 2903 Shepherd, A., D. Wingham and E. Rignot (2004). Warm ocean is eroding West 2904

Antarctic ice sheet. Geophys. Res. Lett. 31, L23402, 2905 doi:10.1029/2004GL021106. 2906

Siniff, D. B., R. A. Garrott, J. J. Rotella, W. R. Fraser, and D. G. Ainley. 2008. 2907 Opinion Projecting the effects of environmental change on Antarctic seals. 2908 Antarctic Science 20:425-435. 2909

Sici�ski, J.; Ja�d�ewski, K.; De Broyer, C.; Ligowski, R.; Presler, P.; Nonato, E.F.; 2910 Corbisier, T.N.; Petti, M.A.V.; Brito, T.A.S.; Lavrado, H.P.; B�a�ewicz- 2911 Paszkowycz, M; Pabis, K; Ja�d�ewska, A. & Campos, L.S. Admiralty Bay 2912 Benthos Diversity: a long-term census. Submitted to Deep-Sea Research Part 2913 II, Census of Antarctic Marine Life special volume. 2914

Smale, D. (2008) Ecological traits of benthic assemblages in shallow Antarctic 2915 waters: does ice scour disturbance select for small, mobile, secondary 2916 consumers with high dispersal potential? Polar Biology 31: 1225-1231 2917

Smith, C.R.; Mincks, S. & DeMaster, D.J. 2008. The FOODBANCS project: 2918 Introduction and sinking fluxes of organic carbon, chlorophyll-a and 2919 phytodetritus on the western Antarctic Peninsula continental shelf. Deep-Sea 2920 Research II 55: 2404–2414. 2921

Smith, C.R.; Mincks; S. & DeMaster, D.J. 2006. A synthesis of bentho-pelagic 2922 coupling on the Antarctic shelf: Food banks, ecosystem inertia and global 2923 climate change. Deep-Sea Research II 53: 875–894. 2924


80

Snape, I.; Riddle, M.J.; Stark, J.S.; Cole, C.M.; King, C.K.; Duquesne, S. & Gore, 2925 D.B. 2001. Management and remediation of contaminated sites at Casey 2926 Station, Antarctica. Polar Res. 37(202): 199-214. 2927

Sokolov, S. and S. R. Rintoul, 2007. Multiple jets of the Antarctic Circumpolar 2928 Current south of Australia. Journal of Physical Oceanography, 37, 1394-1412. 2929

Sokolov, S. and S. R. Rintoul, 2009. The circumpolar structure and distribution of the 2930 Antarctic Circumpolar Current fronts. Part 1: Mean circumpolar paths. 2931 Journal of Geophysical Research – Oceans, 114, C11, 2932 doi:10.1029/2008JC005108 . 2933

Sokolov, S. and S. R. Rintoul, 2009. The circumpolar structure and distribution of the 2934 Antarctic Circumpolar Current fronts. Part 2: Variability and relationship to 2935 sea surface height. Journal of Geophysical Research – Oceans, 114, C11, 2936 doi:10.1029/2008JC005248. 2937

Speer, K., S. R. Rintoul, and B. Sloyan, 2000. The diabatic Deacon cell. Journal of 2938 Physical Oceanography, 30, 3212-3222. 2939

Speich S., B. Blanke, P. de Vries, K. Döös, S. Drijfhout, A. Ganachaud, and R. 2940 Marsh, 2002 : Tasman leakage : a new route in the global ocean conveyor belt. 2941 Geophys. Res. Lett., 29, 10, 10.1029/2001GL014586. 2942

Stammerjohn, SE; Smith, RC, 1997. Opposing southern ocean climate patterns as 2943 revealed by trends in regional sea ice coverage. Climatic Change, 37, 617-639 2944

Stammerjohn SE, Martinson DG, Smith RC, Yuan X, Rind D (2008) Trends in 2945 Antarctic annual sea ice retreat and advance and their relation to El Nino-2946 Southern Oscillation and Southern Annular Mode variability. Journal of 2947 Geophysical Research-Oceans 113. 2948

Stark, J. S.; Snape, I.; Riddle, M.J. & Stark, S. C. 2005. Constraints on spatial 2949 variability in soft-sediment communities affected by contamination from an 2950 Antarctic waste disposal site. Marine Pollution Bulletin 50: 276–290. 2951

Stark, J.S.; Riddle, M.J.; Snape, I. & Scouller, R.C. 2003. Human impacts in Antarctic 2952 marine soft-sediment assemblages: correlations between multivariate 2953 biological patterns and environmental variables at Casey Station. Estuarine, 2954 Coastal and Shelf Science 56: 717–734. 2955

Strass, V. H. and E. Fahrbach, 1998. Temporal and regional variation of sea ice draft 2956 and coverage in the Weddell Sea obtained from upward looking sonars. In 2957 Jeffries, M.O. ed. Antarctic sea ice: physical processes, interactions and 2958 variability. Washington DC, American Geophysical Union, 123-139 2959 (Antarctic Research Series 74) 2960

Summerhayes, C.P., 2007, Global Ocean Monitoring Programs in the Southern 2961 Ocean. In Riffenburgh, B., ed., Encyclopedia of the Antarctic, v.1, Routledge, 2962 London.467-8 2963

Summerhayes, C.P., Dickson, B., Meredith, M., Dexter, P., and Alverson, K., 2007, 2964 Observing the Polar Oceans During the International Polar Year and Beyond. 2965 WMO Bull., 56 (4), 270-28 2966

Summerhayes, C.P., 2004, The Global Ocean Observing System (GOOS) in the 2967 Antarctic Context. In M. Colacino (ed.), Proc SCAR Workshop on 2968 Oceanography, Rome, Italy, 22-24 October 2003. Conference Proceedings 2969 v.89., Italian Physical Society, Bologna.281-290. 2970

Teixidó, N., Garrabou, J., Gutt, J., Arntz, W.E. 2007.Iceberg disturbance and 2971 successional spatial patterns: the case of the shelf Antarctic benthic 2972 communities, Ecosystems, 10(1), 143-158, doi:10.1007/s10021-006-9012-9 . 2973


81

Thompson, D. W. J., and S. Solomon. 2002. Interpretation of recent Southern 2974 Hemisphere climate change. Science 296:895-899. 2975

Thompson, D. W. J., J. M. Wallace, and G. C. Hegerl. 2000. Annular modes in the 2976 extratropical circulation. Part II: Trends. Journal of Climate 13:1018-1036. 2977

Thorndike, D. A., Y. Yu and G. A Maykut, 1999. Thinning of the Arctic sea-ice 2978 cover, Geophys. Res. Lett. 26(23), 3469-3472 2979

Tortell, P. D., C. D. Payne, Y. Li, S. Trimborn, B. Rost, W. O. Smith, C. Riesselman, 2980 R. B. Dunbar, P. Sedwick, and G. R. DiTullio (2008), CO2 sensitivity of 2981 Southern Ocean phytoplankton, Geophys. Res. Lett., 35, L04605, 2982 doi:10.1029/2007GL032583. 2983

Trathan PN, Forcada J, Murphy EJ (2007b) Environmental forcing and Southern 2984 Ocean marine predator populations: effects of climate change and variability. 2985 Philosophical Transactions of the Royal Society B-Biological Sciences 2986 362:2351-2365. 2987

Trathan PN, Murphy EJ, Forcada J, Croxall JP, Reid K, Thorpe SE (2006) Physical 2988 forcing in the southwest Atlantic: ecosystem control. In: Boyd IL, Wanless S, 2989 Camphuysen CJ (eds) Top Predators in Marine Ecosystems. Cambridge 2990 University Press. 2991

Treguer, P. and G. Jacques, 1992. Dynamics of nutrients and phytoplankton, and fluxes of 2992 carbon, nitrogen and silicon in the Antarctic Ocean. Polar Biology, 12, 149-162. 2993

Turner J, Bindschadler R, Convey P, di Prisco G, Fahrbach E, Gutt J, Hodgson D, 2994 Mayewsky P, Summeerhayes C (2009) Antarctic Climate Change and the 2995 Environment. SCAR, Scott Polar Research Institute, Cambridge; 526pp 2996

Turner, J., J. C. Comiso, G. J Marshall, T. A. Lachlan-Cope, T. Bracegirdle, T. 2997 Maksym, M. P. Merideth, Z. Wang, and A. Orr (2009). Non-annular 2998 atmospheric circulation change induced by stratospheric ozone depletion and 2999 its role in the recent increase of Antarcic sea ice extent, Geophys. Res. Lett. 3000

Vaughan, D. G., G. J. Marshall, W. M. Connolley, C. Parkinson, R. Mulvaney, D. A. 3001 Hodgson, J. C. King et al. 2003. Recent rapid regional climate warming on the 3002 Antarctic Peninsula. Climatic Change 60:243-274. 3003

Vázquez-Rodríguez M., Touratier F., Lo Monaco C., Waugh D., Padin X.A., Bellerby 3004 R.G.J., Goyet C., Metzl N., Ríos A.F., Pérez F.F., 2009. Anthropogenic 3005 carbon in the Atlantic Ocean: comparison of four data-based calculation 3006 methods, Biogeosciences, 6, 439-451. 3007

Verdy, A., S. Dutkiewicz, M. J. Follows, J. Marshall, and A. Czaja (2007), Carbon 3008 dioxide and oxygen fluxes in the Southern Ocean: Mechanisms of interannual 3009 variability, Global Biogeochem. Cycles, 21, GB2020, 3010 doi:10.1029/2006GB002916. 3011

Wadhams, P., M. A. Lange, and S. F. Ackley, 1987. The ice thickness distribution 3012 across the Atlantic sector of the Antarctic Ocean in midwinter, J. Geophys. 3013 Res., 92(C13), 14535-14552 3014

Waluda CM, Trathan PN, Rodhouse PG (1999) Influence of oceanographic variability 3015 on recruitment in the Illex argentinus (Cephalopoda : Ommastrephidae) 3016 fishery in the South Atlantic. Marine Ecology-Progress Series 183:159-167. 3017

Waters KJ, Smith RC (1992) Palmer LTER: a sampling grid for the Palmer LTER 3018 program. Antarct J US 27:236–239 3019

Watkins, AB; Simmonds, I, 2000. Current trends in Antarctic sea ice: The 1990s 3020 impact on a short climatology. J. Clim., 13, 4441-4451. 3021


82

Watson, A.J., Boyd, P.W., Turner, S.M., Jickells, T.D. and Liss, P.S. 2008. Designing 3022 the next generation of ocean iron fertilization experiments. Marine Ecology 3023 Progress Series 364:303-309. 3024

Weimerskirch, H. Inchausti, P., Guinet, C. and Barbraud, C. 2003. Trends in bird and 3025 seal populations as indicators of a system shift in the Southern Ocean. 3026 Antarctic Science 15:239-256. 3027

Wilson, P. R., D. G. Ainley, N. Nur, S. S. Jacobs, K. J. Barton, G. Ballard et al., 2001. 3028 Adélie penguin population change in the Pacific sector of Antarctica: relation 3029 to sea ice extent and the Antarctic Circumpolar Current. Marine Ecology 3030 Progress Series, 213, 301-330, doi:10.3354/MEPS213301. 3031

Wong, A. P. S., N. L. Bindoff, and J. Church. 1999. Large-scale freshening of 3032 intermediate waters in the Pacific and Indian Oceans. Nature 400:440-443. 3033

Worby, A. P., C. Geiger, M. J. Paget, M. van Woert, S. F Ackley, T. DeLiberty, 3034 (2008). Thickness distribution of Antarctic sea ice. J. Geophys. Res., 113, 3035 C05S92, doi:10.1029/2007JC004254. 14 pp. 3036

Worby, A. P., G. M. Bush and I. Allison. 2001. Antarctic sea ice thickness 3037 distribution as determined from a moored Upward Looking Sonar. Ann 3038 Glaciol., 33, 177-180. 3039

Wunsch 1996 3040 Yu, Y., G. A. Maykut, an dD. A. Rothrock, 2004. Changes in the thickness 3041

distribution of Arctic sea ice between 1958-1970 and 1993-1997, J. Geophys. 3042 Res., 109, C08004, doi:10.1029/2003JC001982 3043

Yuan, XJ; Martinson, DG, 2000. Antarctic sea ice extent variability and its global 3044 connectivity. J. Clim., 13, 1697-1717. 3045

Zenk, W. and Morozov, E., 2007. Decadal warming of the coldest Antarctic Bottom 3046 Water flow through the Vema Channel. Geophysical Research Letters, 3047 34(L14607): 10.1029/2007GL030340. 3048

Zhang, J. L., 2007. Increasing Antarctic sea ice under warming atmospheric and 3049 oceanic conditions. Journal of Climate, 20, 2515-2529. 3050

Zhang, H-M, Reynolds WR, T M Smith. 2006. Adequacy of the In Situ Observing 3051 System in the Satellite Era for Climate SST. Journal of Atmospheric and 3052 Oceanic Technology, 23, 107-120 3053

Zickfield, K., 2007. Response of the global carbon cycle to human-induced changes 3054 in the Southern Hemisphere winds, Geophys. Res. Lett.., 34, L12712. 3055

Zwally et al., 2002 3056

Date post:	20-May-2020
Category:	Documents
Upload:	others
View:	4 times
Download:	0 times

The Southern Ocean Observing System: Initial Science and ... · Southern Ocean and its role in the...

Documents