Ice Shelf Drilling and Ocean Cavity Exploration Robert Bindschadler, Code 614, NASA GSFC Robert Bindschadler led a successful Antarctic field campaign (November 9 – December 10) to Windless Bight, Antarctica, involving co- investigators from NASA JPL, Naval Postgraduate School and the University of Alaska. The objectives of drilling through a 200-m thick ice shelf, visually exploring the ice with a video camera system and deploying a new ocean profiling system to monitor the sub-shelf ocean properties were all achieved. These tasks were undertaken to prepare for a similar set of activities on the Pine Island Glacier (PIG) ice shelf in 2011-12. The project is jointly funded by NASA and NSF as a key scientific study of the International Polar Year. The field team were able to obtain the first-ever Figure 3: Alberto Behar (JPL) with Borehole camera. Figure 5: Tim Stanton (r) and Jim Stokel (l) (both NPS) with ocean profiler. Figure 2: Martin Truffer (UAF) and hot water drill. Figure 1: Transmission tower. Figure 4: First-ever view of ice shelf base. View includes borehole bottom and Lyssianasid amphipod. rospheric and Biospheric Sciences Laboratory
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Ice Shelf Drilling and Ocean Cavity ExplorationRobert Bindschadler, Code 614, NASA GSFC
Robert Bindschadler led a successful Antarctic field campaign (November 9 – December 10) to Windless Bight, Antarctica, involving co-investigators from NASA JPL, Naval Postgraduate School and the University of Alaska. The objectives of drilling through a 200-m thick ice shelf, visually exploring the ice with a video camera system and deploying a new ocean profiling system to monitor the sub-shelf ocean properties were all achieved. These tasks were undertaken to prepare for a similar set of activities on the Pine Island Glacier (PIG) ice shelf in 2011-12.
The project is jointly funded by NASA and NSF as a key scientific study of the International Polar Year. The field team were able to obtain the first-ever photograph of the underside of an ice shelf and were surprised to see higher life forms (both a Lyssianasid amphipod and tentacles from a jellyfish) more than 20 kilometers from seasonally open water.
Figure 3: Alberto Behar (JPL) with Borehole camera.
Figure 5: Tim Stanton (r) and Jim Stokel (l) (both NPS) with ocean profiler.
Figure 2: Martin Truffer (UAF) and hot water drill.
Figure 1: Transmission tower.
Figure 4: First-ever view of ice shelf base. View includes borehole bottom and Lyssianasid amphipod.
Hydrospheric and Biospheric Sciences Laboratory
Name: Robert Bindschadler, NASA/GSFC E-mail: [email protected]: 301-614-5707
Technical Description of Image:Figure 1: Tower holding surface data transmission package that receives ocean profiler data from beneath the ice shelf and phones data back to Naval Postgraduate School. Wind generator provides power. Guy lines are required to stabilize the tower in high winds
Figure 2: Dr. Martin Truffer of University of Alaska with the 8-inch diameter reaming head of the hot-water drilling system. This probe widens the hole to a diameter that allows the profiler to pass through the ice shelf into the water below.
Figure 3: Dr. Alberto Behar of Jet Propulsion Laboratory preparing to deploy his customized borehole camera system. The housing contains downward and side-looking cameras as well as lights to illuminate the dark recesses of the ice shelf and the water below. An additional camera was attached to the cable and pointed upwards to capture views of the underside of the ice shelf.
Figure 4: Unique view of the underside of the McMurdo ice shelf. The scalloped inner wall of the hot-water drilled hole is visible as well as the remarkably smooth underside of the ice shelf. An exciting discovery was the presence of the approximately 3-inch long amphipod that swam by—presumably attracted by the lights of the camera
Figure 5: Drs. Tim Stanton (left), Martin Truffer (center) and James Stokkel (right) preparing the first-ever sub-ice shelf ocean profiler for its one-way deployment through the ice shelf and into the800-meter deep ocean cavity below. Stanton and Stokkel are from the Naval Postgraduate School, Monterey, CA.
Scientific significance: Ocean heat accessing the underside of floating ice shelves is widely believed to be the primary cause of recent increases of ice sheet mass loss accelerating sea level rise. Direct measurements of the sub-shelf ocean properties are mandatory but extremely difficult. The joint NASA-NSF International Polar Year project is scheduled to initiate such measurements at the Pine Island Glacier, the site of the largest ice sheet changes, in the 2011-12 field season. The work this field season in Windless Bight (near McMurdo Station) was designed to test all phases of the drilling, video-exploration and ocean profiling to reduce risk when the field team is able to reach Pine Island Glacier. These measurements will begin a unique sustained view of ocean-ice interaction.
Relevance for future science and relationship to Decadal Survey: Ocean-ice interaction is the key process driving rapid ice loss, but is not understood sufficiently to permit prediction of future sea level. The importance of this process was revealed primarily from NASA satellite observations of ice sheets. Continued satellite observations, primarily ICESat-2 (and IceBridge) and DESDynI will provide critical corroborative data to accompany the unique sub-ice shelf measurements provided by this projects ocean profilers.
Hydrospheric and Biospheric Sciences Laboratory
Comparison of satellite and surface temperatures Comparison of satellite and surface temperatures at Summit, Greenland
Lora S. Koenig, NASA/GSFC, Code 614.1
Since 1950 average annual near-surface air temperatures in the Arctic have risen by 2 to 3 °C with winter-time temperatures rising by up to 4 °C (ACIA, 2005). This research compares surface and near-surface air temperatures to Moderate Resolution Imaging Spectroradiometer (MODIS)-derived land-surface temperatures (LSTs) during the boreal winter of 2008-2009 at Summit, Greenland.
During this study MODIS LSTs were consistently lower than the thermochron-measured surface temperatures by ~3°C. The winter-time mean MODIS LST was 11.0 °C lower than the winter-time mean near-surface air temperature, largely because MODIS LSTs cannot be measured through cloud cover. The implications of this work are far reaching because of the great need to accurately measure the temperature trends of the Greenland Ice Sheet for determination and quantification of Arctic warming.
Figure 1: Picture of the paired thermochrons measuring snow surface temperatures.
Figure 2: Comparison of surface temperature to MODIS LST for the area over Summit, Greenland.
Arctic Climate Impact Assessment (ACIA). 2005. An Introduction to the Arctic Climate Impact Assessment. In Carolyn Symon and others, eds. Arctic Climate Impact Assessment. Cambridge, Cambridge University Press, 1-29.
Koenig, LS. and DK Hall. (Submitted). Comparison of satellite, thermochron and station temperatures at Summit, Greenland, during the winter of 2008-09. Journal of Glaciology .
Technical Description of Image:Figure 1: Picture of thermochrons placed on the snow surface to obtain snow surface temperature comparable to temperatures derived from infrared satellite sensors. Thermochron sensors are small self-sufficient digital thermometers and data loggers that operate over a temperature range from -40 to +85 °C, and can store approximately 11 months of hourly temperature data.
Figure 2: Comparison of surface temperature to MODIS LST for the area over Summit, Greenland. On average the MODIS land-surface temperatures (LST) underestimated the surface temperatures by 3.1 °C. The large gap in data between ~-32 to -22 °C is caused because clouds (as determined by the MODIS cloud mask) precluded LST measurements during winter storms in which surface and air temperatures increased. The cloud mask acted as a temperatures mask explaining the larger error of 11.0 °C, when using MODIS LSTs to measure the mean seasonal temperature compared to the mean seasonal temperature from surface air temperatures.
Scientific significance: Temporally and spatially accurate temperature measurements are necessary over ice sheets to determine temperature trends. To accurately calibrate, validate and characterize sub-pixel variability of remote sensing temperature retrievals over large expanses of the ice sheets, a need exists for a rugged, low-cost, autonomous, reliable instruments that are easily deployable, such as a thermochron sensors. This is the first study using thermochron sensors successfully during a winter season on an ice sheet. This study showed the thermochrons have high accuracy and shows their utility for calibrating and validation satellite measurements. This study showed a large difference between winter-time near-surface temperatures and satellite-derived LSTs. Since LSTs are not acquired through cloud cover from space, the seasonal mean is not representative of the ground-based station seasonal mean; this result likely holds for all of Greenland.
Relevance for future science and relationship to Decadal Survey: Understanding recent temperatures trends and predicting future trends over the ice sheets is critical for predicting future sea level rise. Our ability to understand temperature trends relies on a firm understanding of how satellite-derived LSTs relate to near-surface temperatures over the ice sheets. This research takes steps towards understanding mean winter-time temperature differences, caused by the cloud masking of warm winter storms, that arises between LSTs and near-surface measurements.
Hydrospheric and Biospheric Sciences Laboratory
Effect of Topography on Remote Sensing at L-BandDavid LeVine, Code 614.2, NASA GSFC
Topography can be important for passive microwave remote sensing of soil moisture from space. A problem in assessing the importance of topography is that a digital elevation model for the surface (e.g. Fig 1) does not provide an intuitive estimation of when topography will be important. This is especially true given the large footprint (40-100 km) of L-band radiometers in space such as SMOS, Aquarius and SMAP.
To address this issue, the DEM has been replaced with a probability density function (pdf) for slopes. The slope pdf separates into ``smooth'' and ``rough'' distributions that correlate with the effect of topography on radiometric brightness temperature.
The model has been applied to the site of the soil moisture experiment, SMEX04 (Fig 1). Fig 2 shows the effect of topography on brightness temperature and a comparison of the model results with direct calculations using the DEM .
Figure 1: LandSat image of the site of SMEX04 (Tombstone, Arizona)
Figure 2: Effect of topography at L-band for horizontal (H) and vertical (V) polarization.
Hydrospheric and Biospheric Sciences Laboratory
Name: David M. Le Vine, NASA/GSFC, Code 614.2Email: [email protected]: 301-614-5640
References: Utku, C. and D.M. Le Vine, “Topographic Effects on Brightness Temperature at L-band”, Proc. International Union of Radio Science (URSI), General Assembly, Chicago, IL, August, 2008. Utku, C. and D.M. Le Vine, “A Model for Prediction of the Impact of Topography on Microwave Emission”, IEEE Transactions on Geoscience and Remote Sensing, accepted pending minor changes, 2010.
Data Sources: The soil moisture experiment, SMEX-04, with sites in Arizona (Tombstone) and Mexico (Sonora) to develop algorithms for remote sensing of soil moisture, including effects of topography and land cover. Goddard flew the L-band radiometer 2D-STAR.
Descriptions of Figures Figure 1 is a false color LandSat image of the Arizona site of the SMEX04 soil moisture experiment. The region was divided into three regions (yellow boxes) corresponding to “low”, “medium” and “high” topographic relief. Figure 2 shows the effect of topography on the L-band radiometric (i.e. passive) signal at horizontal (blue) and vertical polarization (red). The solid line is the model prediction and the symbols represent direct computation from the associated digital elevation map. ∆TB (vertical axis) is the change relative to a flat surface and is plotted as a function of viewing angle. For reference, the local incidence angle of the outer Aquarius beam is near 45 degrees and SMAP is planned for 40 degrees. The model, which is based on the distribution of slopes, consists of two probability distributions with parameters that can be associated with small and large effect on radiometric brightness (TB). The advantage of the new work is the direct relationship to the expected change in brightness temperature, ∆TB.
Relevance for future science and relationship to Decadal Survey: Passive microwave remote sensing from space at L-band (1.4 GHz) is important for global monitoring of soil moisture, sea surface salinity and will be useful in the cryosphere. Several L-band missions are on the way: SMOS, was launched by ESA in November; Aquarius is scheduled for the end of 2010; and SMAP, a decadal survey instrument, is under development. The effect of topography on the passive signal is an important issue for land applications at L-band. Analysis indicates effects as large as 5-10 K at incidence angles employed in these missions. Research is underway at GSFC to quantify the effect and develop a model that will help determine when topography is an important issue to take into account. Theoretical work will be validated using SMOS and Aquarius data and should be ready to improve remote sensing of soil moisture with SMAP.
Earth Science Picture of the Day: Aureole from Mauna Kea
James Foster, Code 614.3, NASA GSFC
• Photographer: David K. Lynch: Summary Author: David K. Lynch • The aureole is a bright, white glow around the Sun or Moon. It’s almost always present and is due to forward scattering of
sunlight from small aerosol particles. Such particles may be tiny water droplets, haze or dust, smog droplets, pollen, or volcanic dust. Any tiny surface can create them, and I’ve even seen aureoles caused by a cloud of mosquitoes! Air molecules do not produce aureoles.
• In the picture at left, an aureole is seen around the Sun, which is hidden behind a light fixture. This was an exceptionally clear day with almost no dust in the air, so the aureole is small. In most cases, the aureole is many times larger. The picture at right was taken the next day when there was no detectable aureole, a rarity. As hard as it may be to believe, the Sun is actually behind the light fixture! The two bright spots are due to diffraction of the hidden solar disk by the edges of the light’s metal housing. Both photos were taken from Mauna Kea, Hawaii. I’ve only seen three days when it was this clear, and each was at Hale Pohaku, the astronomer’s community on Mauna Kea. Such clarity only occurs at high altitudes. From low elevations – specifically in the planetary boundary layer – there are always significant amounts of aerosols, and thus the aureole is always present.
• Hale Pohaku (aka Onizuka Center for International Astronomy) coordinates: 19.760833, -155.455278
Figure 1: (Left) Detectable aureole from Mauna Kea and (Right) no detectable aureole from Mauna Kea
The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives.
Hydrospheric and Biospheric Sciences Laboratory
Data Source/Website: http://epod.typepad.com/blog/
Purpose/Use of Images: The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery. When possible, EPOD links views from the Earth to views of the Earth, utilizing the Earth Observatory and Visible Earth.
Description of Figures: Figure 1: In the picture at left, an aureole is seen around the Sun, which is hidden behind a light fixture. This was an exceptionally clear day with almost no dust in the air, so the aureole is small. In most cases, the aureole is many times larger. The picture at right was taken the next day when there was no detectable aureole, a rarity.
Scientific significance: As part of its education and public outreach initiatives, the NASA Earth Sciences Division provides freely-available views of the Earth, on both small and large scales, of Earth Science research through web-based publications such as EPOD and the Earth Observatory. EPOD shares with the general public the images, stories, and anecdotes of everything from atmospheric optics to roadside geology. The following slide is a sample of the EPODs featured during the last 9 ½ years.
Relevance: Education and public outreach are important components of each of the NASA enterprises. The Earth Science picture of the day provides an invaluable resource into how NASA and its partners do research in order to better understand our planet.
Hydrospheric and Biospheric Sciences Laboratory
Name: James Foster, NASA GSFCE-Mail: [email protected]: 301-614-5769
