Antarctic Sea Ice Variability 1979-2006Antarctic 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 passivemicrowave radiometers for the 28-year period 1979-2006 show an increase of1.0 + 0.4% per decade. This overall increase results from contrasting trendsin five regional sectors: the Weddell Sea, the Indian Ocean, the WesternPacific Ocean, the Ross Sea, and the Bellingshausen/Amundsen seas. Themost striking feature of this figure is how different the monthly trend patternsare for the five sectors. The Weddell Sea and Western Pacific Ocean havemostly positive trends, with the largest positive values occurring during thefirst half of the year. The Indian Ocean sector also has mostly positive trendsbut has its largest values during the last half of the year. The Ross Sea haspositive trends for all twelve months and for most months has the largestpositive trends of all five sectors. Only the Bellingshausen/Amundsen Seassector has negative trends for each month, with the largest negative trends inDecember, January, and February. For the Southern Hemisphere as a wholeall twelve months exhibit positive trends, with the smallest occurring inDecember and the largest in May.
Figure 2: Seasonal variation in sea ice coverage is significant, increasing from a minimumin February to a maximum in September
Figure 1: Thefive regionalsectors: theWeddell Sea,the IndianOcean, theWestern PacificOcean, the RossSea, and theBellingshausen/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 SouthernHemisphere as a whole
Names: Donald J. Cavalieri and Claire L. Parkinson, NASA GSFC
Emails: Donald.J.Cavalieri@nasa.gov and Claire.L.Parkinson@nasa.gov
Phones: 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, submittedSeptember 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 MultichannelMicrowave 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 ofaverage 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% perdecade. This contrasts with the much greater decrease in the Arctic sea ice cover for the same period (Parkinsonand Cavalieri, 2007). A possible reason for an increasing ice cover in the Southern Hemisphere under warmingatmospheric and oceanic conditions has been suggested by Zhang (2007) based on a modeling study. Thesuggested mechanism involves reduced convective overturning in the ocean beneath the ice and hence reducedocean heat flux available to melt ice, resulting in an overall increase in ice extent and volume.
The Fourth SeaWiFS HPLC Analysis Round-Robin Experiment(SeaHARRE-4): A Novice’s PerspectiveThe Fourth SeaWiFS HPLC Analysis Round-Robin Experiment(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- andmulti-point regressions of known standards to create a calibration table, used to identifyphytoplankton pigments in unknown samples. Pigment samples from twelve coastal oceanicenvironments were analyzed in triplicate at each laboratory. Using SeaHARRE establishedperformance metrics, and the Van Heukelum and Thomas (2001) method, GSFC obtainedstate-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
Figure 1: The points on this graph representinjections of five chlorophyll a standards ofknown concentrations, used to calibrate theHPLC instrument. Placement of the pointsdirectly on the line, resulting in a R2 equal to1.0000, signifies the accuracy of the instrument.
Figure 2: Chromatogram for a SeaHARRE-4 sample. Theoutlined peak is chlorophyll a, the main pigment found in mostphytoplankton, small photosynthetic organisms which are thebasis of the marine food-web. The size of the area under thecurve reflects the concentration of chlorophyll a in the sample.
SeaHARRE sample 36B at 665nm
Peak Area (mAU)
minutes
Name: Stan Hooker, NASA GSFC and Mary Elizabeth Russ, UMBC/GEST/NASA GSFC
E-mail: meruss@neptune.gsfc.nasa.gov
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 PostlaunchTechnical 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-RobinExperiment (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 oceanicbiogeochemical 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 ofphytoplankton 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, fromeach 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 oneregression 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 differentpigments 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 naturalSeaHARRE samples. Chlorophyll a is shown here because this pigment is the basis for satellite ocean color calculations, and the chromatograph also demonstrates thepotential 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, withonly past NASA SeaHARRE memorandums and a well established HPLC method (currently used by Horn Point Laboratory (HPL)), as a guide, illustrates the success of theperformance 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 forcalibration and validation activities. Future SeaHARRE round robins will continue to focus on ecologically complex coastal regions, and more extensively define the pigmentdynamics in these areas. The successful template constructed by the SeaHARRE workshops will also be applied to other optical and biogeochemical measurements utilized forcalibration and validation activities. By this approach, uncertainties will be defined and protocols written, which will provide community accepted performance metrics for othermeasurements. These metrics will serve as guidelines to assure that data used for calibration and validation purposes by the research community, and stored within theSeaWiFS Bio-optical Archive and Storage System (SeaBASS), is quality-assured data, and appropriate to use in satellite data analysis and interpretation.
Hydrospheric and Biospheric Sciences Laboratory