Antarctic sea ice trends and its response to the Southern annular mode
Sea ice covers vast regions of the Southern Ocean and impacts on the climate as well as the plant and animal life of the region. The variability of sea ice in the Southern Ocean affects the entire food web of the region, from phytoplankton to Antarctic krill through to the apex predators such as seals and penguins. Sea ice variability is determined by shifts in the atmospheric temperature distribution and shifts in the atmospheric circulation. The Southern Annular Mode (SAM) is the primary mode of variability in the atmospheric circulation of the Southern Hemisphere. Despite the overall warming of Antarctica, sea ice extent and sea ice area show a positive trend in the Southern Ocean and all its sectors except in the Bellingshausen/Amundsen Seas sector which displays a negative trend for the period 1979-2007. The SAM index also shows a positive trend during this period indicating a shift towards the more positive phase. The monthly and seasonal correlations between the SAM index and sea ice concentrations display a dipole, with more ice occurring in the Ross Sea during the positive phase of SAM and less ice occurring in the Weddell Sea.
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