Interpretation of recent Antarctic sea ice variability

Trends in the satellite-derived Antarctic sea ice concentrations (1979-2002) show pronounced increase (decrease) in the central Pacific sector (Bellingshausen/western Weddell sector) by similar to4-10% per decade. Confidence levels for these regional trends exceed 95%. Positive polarities of the Antarctic Oscillation (AAO) lead to more (less) ice in the eastern Ross/Amundsen sector (Bellingshausen/northern Weddell sector), which are qualitatively opposite to the impacts of positive polarities of the El Nino-Southern Oscillation (ENSO). The mechanisms responsible for the covariability between the ice and the (a) AAO and (b) ENSO are demonstrated. Over the last 24 years, a positive AAO trend and a slightly negative ENSO trend produce a spatial pattern of ice changes similar to the regional ice trends. However, the magnitude of the ice changes associated with the AAO and ENSO is much smaller than the regional ice trends. More local (or less understood large) scale processes should be investigated for the explanations.