ANTARCTIC SEA ICE VARIATIONS AND SEASONAL AIR-TEMPERATURE RELATIONSHIPS

Monthly Antarctic station temperatures are used in conjunction with grids of sea ice coverage in order to evaluate the temporal trends and the strength of associations between the two variables at lags of up to several seasons. Over the 30-year period 1958-1987 the trends of temperature are positive in all seasons. However, for the 15 years (1973-1987) for which ice data are available, the trends of temperature are predominantly positive only in winter and summer. The trends are most strongly positive over the Antarctic Peninsula. The spatially aggregated trend of temperature for this latter period is small but positive, while the corresponding trend of ice coverage is small but negative. Regional trends of both variables are larger. Cross correlations between concurrent anomalies of the two variables are negative over most of the continent and are strongest over the Antarctic Peninsula, especially in winter. Lag correlations between seasonal anomalies of the two variables are generally stronger with ice lagging the summer temperatures and with ice leading the winter temperatures. The implication is that summer temperatures predispose the near-surface waters to above- or below-normal ice coverage in the following autumn and winter. The conclusions show little dependence on the choice of the sea ice data source or of the measure of sea ice (extent or areal coverage), but they do depend considerably on the method by which the data are geographically aggregated.