Decadal Changes in the Antarctic Sea Ice Cover

J. C. Comiso

NASA Goddard Space Flight Center, Code 971
Greenbelt, MD 20771

The results of trend analysis, using two decades of passive microwave satellite data, reveal a remarkably stable sea ice cover over the southern hemisphere with the ice extent and ice area changing only by 0.4 ± 0.3 %/decade and 1.7 ± 0.3 %/decade, respectively. Regionally, however, large interannual and decadal changes are apparent. For example, the ice extent at the Bellingshausen/Amundsen Seas has been decreasing at a rate of -8.1 ± 1.4 %/decade. This reflects the large change in the physical characteristics of the ice cover in the region, especially at the Bellingshausen Sea. In the latter, much of the region is free of ice during the summer in the 1990s compared to that in the 1980s. This also means that the older and thicker ice types in the region are gradually disappearing. On the other hand, an almost equal but opposite rate of 7.0 ± 1.0 %/decade is observed in the Ross Sea. This may suggest that the ice cover that has been lost in the Bellingshausen/Amundsen Seas has actually migrated to the Ross Sea. The two adjacent regions, however, appear to be under the influence of two different climatic systems since a warming is observed in the adjacent Antarctic Peninsula while a slight cooling is observed in the Ross Ice Shelf region over the last two decades. Although the trend in extent is basically null at the other regions, large spatial changes are also apparent, especially at the the Weddell Sea region. This appears to be partly influenced by big icebergs that calved from the Filchner Ice Shelf. Spatial changes in the annual anomalies in the sea ice cover, with especial emphasis on those of most recent years including 2001, has been evaluated and will be presented.