Antarctic Sea Ice Variability 1979-2006 Antarctic Sea Ice Variability 1979-2006 Donald J. Cavalieri and Claire L. Parkinson, Code 614.1, NASA GSFC Monthly-averaged Antarctic sea ice extents derived from satellite passive microwave radiometers for the 28-year period 1979-2006 show an increase of 1.0 + 0.4% per decade. This overall increase results from contrasting trends in five regional sectors: the Weddell Sea, the Indian Ocean, the Western Pacific Ocean, the Ross Sea, and the Bellingshausen/Amundsen seas. The most striking feature of this figure is how different the monthly trend patterns are for the five sectors. The Weddell Sea and Western Pacific Ocean have mostly positive trends, with the largest positive values occurring during the first half of the year. The Indian Ocean sector also has mostly positive trends but has its largest values during the last half of the year. The Ross Sea has positive trends for all twelve months and for most months has the largest positive trends of all five sectors. Only the Bellingshausen/Amundsen Seas sector has negative trends for each month, with the largest negative trends in December, January, and February. For the Southern Hemisphere as a whole all twelve months exhibit positive trends, with the smallest occurring in December and the largest in May. Figure 2: Seasonal variation in sea ice coverage is significant, increasing from a minimum in February to a maximum in September Figure 1: The five regional sectors: the Weddell Sea, the Indian Ocean, the Western Pacific Ocean, the Ross Sea, and the Bellingshaus en/Amundsen Seas drospheric and Biospheric Sciences Laboratory Figure 3: Sea ice extent trends by month based on the 28-year record for all five sectors and the Southern Hemisphere as a whole
Donald J. Cavalieri and Claire L. Parkinson, Code 614.1, NASA GSFC
Monthly-averaged Antarctic sea ice extents derived from satellite passive microwave radiometers for the 28-year period 1979-2006 show an increase of 1.0 + 0.4% per decade. This overall increase results from contrasting trends in five regional sectors: the Weddell Sea, the Indian Ocean, the Western Pacific Ocean, the Ross Sea, and the Bellingshausen/Amundsen seas. The most striking feature of this figure is how different the monthly trend patterns are for the five sectors. The Weddell Sea and Western Pacific Ocean have mostly positive trends, with the largest positive values occurring during the first half of the year. The Indian Ocean sector also has mostly positive trends but has its largest values during the last half of the year. The Ross Sea has positive trends for all twelve months and for most months has the largest positive trends of all five sectors. Only the Bellingshausen/Amundsen Seas sector has negative trends for each month, with the largest negative trends in December, January, and February. For the Southern Hemisphere as a whole all twelve months exhibit positive trends, with the smallest occurring in December and the largest in May.
Figure 2: Seasonal variation in sea ice coverage is significant, increasing from a minimum in February to a maximum in September
Figure 1: The five regional sectors: the Weddell Sea, the Indian Ocean, the Western Pacific Ocean, the Ross Sea, and the Bellingshausen/Amundsen Seas
Hydrospheric and Biospheric Sciences Laboratory
Figure 3: Sea ice extent trends by month based on the 28-year record for all five sectors and the Southern Hemisphere as a whole
Names: Donald J. Cavalieri and Claire L. Parkinson, NASA GSFCEmails: [email protected] and [email protected]: 301-614-5901 and 301-614-5715
Full Reference:Cavalieri, D. J. and C. L. Parkinson, Antarctic sea ice variability 1979-2006, JGR Oceans, submitted September 2007.
Related References:Parkinson, C. L. and D. J. Cavalieri, Arctic sea ice extents, areas, and trends, 1979-2006, JGR Oceans, submitted
September 2007.
Zhang, J., Increasing Antarctic sea ice under warming atmospheric and oceanic conditions, J. Climate, 20, 2515-2529, 2007.
Data Sources:Sea ice extents were derived from satellite passive-microwave data obtained from the Nimbus 7 Scanning
Multichannel Microwave Radiometer (SMMR) and the DMSP F8, F11, and F13 Special Sensor Microwave Imagers (SSMIs).
Technical Description of Figures:
Figure 1: Southern Hemisphere 28-year average ice concentration maps for February and September, the months of average minimum and maximum sea ice extents, respectively.
Figure 2: Southern Hemisphere sector map.
Figure 3: 28-year sea ice extent trends by month for all five sectors and for the Southern Hemisphere as a whole.
Scientific Significance: The overall Southern Hemisphere sea ice extent is increasing at the rate of 1.0 + 0.4% per decade. This contrasts with the much greater decrease in the Arctic sea ice cover for the same period (Parkinson and Cavalieri, 2007). A possible reason for an increasing ice cover in the Southern Hemisphere under warming atmospheric and oceanic conditions has been suggested by Zhang (2007) based on a modeling study. The suggested mechanism involves reduced convective overturning in the ocean beneath the ice and hence reduced ocean heat flux available to melt ice, resulting in an overall increase in ice extent and volume.
The Fourth SeaWiFS HPLC Analysis Round-Robin Experiment The Fourth SeaWiFS HPLC Analysis Round-Robin Experiment (SeaHARRE-4): A Novice’s Perspective(SeaHARRE-4): A Novice’s Perspective
SeaHARRE-4 evaluated a High Performance Liquid Chromatography (HPLC) novice (GSFC) and established HPLC labs. Preparation prior to sample analysis included running single- and multi-point regressions of known standards to create a calibration table, used to identify phytoplankton pigments in unknown samples. Pigment samples from twelve coastal oceanic environments were analyzed in triplicate at each laboratory. Using SeaHARRE established performance metrics, and the Van Heukelum and Thomas (2001) method, GSFC obtained state-of-the-art results, which established the capability of the GSFC laboratory to analyze high-quality pigment data for use in validating satellite derived global chlorophyll concentrations.
Stan Hooker, Code 614.2, NASA GSFC, Mary Elizabeth Russ, Code 614.2, UMBC/GEST/NASA GSFC
Hydrospheric and Biospheric Sciences Laboratory
Chlorophyll a dilution 1 calibration curve1 09172007
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Figure 1: The points on this graph represent injections of five chlorophyll a standards of known concentrations, used to calibrate the HPLC instrument. Placement of the points directly on the line, resulting in a R2 equal to 1.0000, signifies the accuracy of the instrument.
Figure 2: Chromatogram for a SeaHARRE-4 sample. The outlined peak is chlorophyll a, the main pigment found in most phytoplankton, small photosynthetic organisms which are the basis of the marine food-web. The size of the area under the curve reflects the concentration of chlorophyll a in the sample.
SeaHARRE sample 36B at 665nm
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Name: Stan Hooker, NASA GSFC and Mary Elizabeth Russ, UMBC/GEST/NASA GSFC E-mail: [email protected] Phone: 301-286-9150
References:Hooker, S.B., H. Claustre, L. Van Heukelem, J.-F. Berthon, R. Barlow, 2000. The first SeaWiFS HPLC Analysis Round-Robin Experiment (SeaHARRE-1), SeaWiFS Postlaunch Technical Report Series, Volume 14, S.B. Hooker and E.R. Firestone, editors. NASA Technical Memorandum 2000-206892. (http://oceancolor.gsfc.nasa.gov/)
Hooker, S.B., L Van Heukelem, H. Claustre, R. Barlow, L. Schlüter, J. Perl, V. Stuart, L. Clementson, and J. Fishwick, 2005. The second SeaWiFS HPLC Analysis Round-Robin Experiment (SeaHARRE-2). NASA Technical Memorandum 2005-212785. (http://oceancolor.gsfc.nasa.gov/)
Hooker, S. B., C.R. McClain, and A. Mannino, 2007. NASA strategic planning document: A comprehensive plan for the long-term calibration and validation of oceanic biogeochemical satellite data. NASA Technical Memorandum NASA/SP-2007/214152 (http://oceancolor.gsfc.nasa.gov/)
Van Heukelem, L. and C.S. Thomas, 2001. Computer-assisted high-performance liquid chromatography method development with applications to the isolation and analysis of phytoplankton pigments. Journal of Chromatography A, 910, 31-49.
Data Sources:The SeaWiFS HPLC Analysis Round-Robin Experiments (SeaHARRE) are part of the Calibration and Validation Office (http://oceancolor.gsfc.nasa.gov/). For SeaHARRE-4, samples were collected in Danish waters by DHI Water and Environment (http://www.dhigroup.com). Samples, from twelve locations, were collected, and triplicate filters, from each location, were shipped to the ten participating international laboratories for HPLC analysis.
Technical Description of Image:Figure 1: An illustration of the excellent calibration results obtained by GSFC for the multi-point regressions of the working standard chlorophyll a. This graph is an example one regression curve, however, two separate dilutions were performed, on two separate days, using two separate sets of dilution standards. Figure 2: A depiction of a SeaHARRE-4 chromatograph and the peaks resolved at 665 nm. Each peak associated with chlorophyll a is displayed. Standards for twenty different pigments were characterized, and retention times and response factors (Rf) were compiled in a calibration table, which in turn, was used to identify the pigments in the natural SeaHARRE samples. Chlorophyll a is shown here because this pigment is the basis for satellite ocean color calculations, and the chromatograph also demonstrates the potential complexity of a single pigment, which may include other chemical forms of a pigment (allomers or epimers) or degradation products.
Scientific significance:The ability of a novice lab (GSFC - no prior HPLC experience) to perform intricate HPLC pigment analysis and data interpretation, and obtain state-of-the-art performance, with only past NASA SeaHARRE memorandums and a well established HPLC method (currently used by Horn Point Laboratory (HPL)), as a guide, illustrates the success of the performance metrics established by previous SeaHARRE round robins to obtain quality-assured data.
Relevance for future science and relationship to Decadal Survey: Previous SeaHARRE workshops have provided a foundation for collaboration within the HPLC community, resulting in a series of accepted performance metrics, in which HPLC pigment analysis may be assessed, and data identified as quality-assured, and thus, acceptable for calibration and validation activities. Future SeaHARRE round robins will continue to focus on ecologically complex coastal regions, and more extensively define the pigment dynamics in these areas. The successful template constructed by the SeaHARRE workshops will also be applied to other optical and biogeochemical measurements utilized for calibration and validation activities. By this approach, uncertainties will be defined and protocols written, which will provide community accepted performance metrics for other measurements. These metrics will serve as guidelines to assure that data used for calibration and validation purposes by the research community, and stored within the SeaWiFS Bio-optical Archive and Storage System (SeaBASS), is quality-assured data, and appropriate to use in satellite data analysis and interpretation.
