Oceanography of the Amundsen and Bellingshausen Seas

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9418151 Jacobs This project will process, analyze, and report the findings of the previously funded first systematic oceanographic study of the continental shelves of the Amundsen and Bellingshausen Seas, which included temperature and salinity profiling, water sampling for ocean chemistry, and continuous precision bathymetry. Upwelling warm deep water covers the Amundsen and Bellingshausen shelves and was found to deliver significant amounts of heat to the sea ice and fringing ice shelves. The regional precipitation is heavy, and has historically maintained a perennial ice cover. However, within the last few years satellite images have shown that the ice has been receding dramatically, with large areas of open water persisting through the winter in sectors that earlier had been ice-covered. These anomalous ice distributions are likely to have been accompanied by altered surface water properties, and possibly changes in the deep vertical circulation. There are indications that the conditions favoring a reduction in the sea ice may migrate westward toward the Ross Sea, and may have influenced a gradual wapming over recent decades on the western side of the Antarctic Peninsula. The current project will investigate the production of shelf water and deep water through interactions with coastal polynyas and floating ice, and make use of a large body of ancillary data on the geochemical, biological, and cryospheric environment. The project made use of the R/V Nathaniel B. Palmer in two cruises: one in the late austral summer 1993-1994, and a subsequent cruise in September and October to observe late winter conditions. ***