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Abstract SOUTHERN OCEAN PRIMARY PRODUCTIVITY: A VIEW TO THE FUTURE Walker O. Smith, Jr.1 and Josefino
C. Comiso2 Estimates of primary production have been historically hampered by the Antarctic’s remoteness, cloud cover, and great size, and as a result, great uncertainty exists in the estimates of primary production over selected regions of the Antarctic or for the entire Southern Ocean. Historical estimates of productivity are reviewed, and a satellite view of the Southern Ocean productivity is presented. Productivity is estimated using a vertically generated production model, in conjunction with satellite-derived water temperatures, pigment concentrations, cloud cover, and modeled irradiance and photoperiods. The waters of the Antarctic are extremely unproductive on an annual basis, as much of the system has near zero production over half of the year due to the limited amounts of irradiance. Certain regions appear to be much more productive than others; for example, the continental shelves of the Ross and Weddell Seas, areas of polynyas, are more productive than other regions. Like other oceanic regions, the waters of the continental shelf are generally more productive that those in deeper waters, and little variations are observed in waters greater than 1,000 m. The temporal patterns of productivity change in selected regions were analyzed to see if the productivity has changed in a manner similar to the known ice concentration changes. Productivity of the Ross Sea is negatively correlated with ice concentrations, suggesting that the increased concentrations observed have reduced productivity in recent years. In contrast, no relationship with ice and productivity was noted in the Weddell Sea. The use of an appropriate model to assess the trends in productivity will allow for an improved understanding of the impacts of regional change on food webs and biogeochemical cycles.
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