Intermediate-scale sea ice - Atmosphere interactions over high southern latitudes in winter

Associations between polar air cloud vortices ("polar lows"), as an indicator of intermediate-scale atmospheric activity, and the Antarctic sea ice, are examined for the Southern Hemisphere winter (June-September). Seven consecutive winters, spanning a period of marked interannual variability of the atmospheric circulation and sea ice (1977-83), are analyzed using sets of DMSP (Defense Meteorological Satellite Program) imagery. Relatively high frequencies of polar lows are found in ice-edge and adjacent ocean latitudes. There is some evidence for an equatorward shift in the latitude of maximum monthly polar low occurrence during the June to September period. Polar low incidence over the Southern Hemisphere on interannual time scales shows a close association with positive sea ice anomalies in the longitudes of more frequent cold air outbreaks from higher latitudes. This is particularly apparent for winters of strongly anomalous circulation, such as FGGE (1979) and the major ENSO of 1982-83. However, for individual cases on daily to weekly time scales, the feedback of cold air - sea ice advance - polar low development is not always evident, and implies that additional processes may contribute to polar air cyclogenesis in the marginal ice zone.