Southern Ocean Sea Ice Processes Associated with the Southern Oscillation

The anomalies in the sea ice cover and the climate of the Southern Ocean and their relationships with the Southern Oscillation (SO) are studied using 17 years of data from 1982 through 1998. We correlate the polar climate anomalies with the Southern Oscillation index (SOI) and examine the composites of these anomalies under three phases of SOI: SOI > 0, 0 > SOI > -1, SOI < -1. The Southern Ocean climate is characterized by anomalies in sea-level pressure, wind, surface air temperature, and sea surface temperature while the Antarctic sea ice cover is characterized by anomalies in its extent, concentration, motion, and ice surface temperature. The fields of monthly mean ice motion and ice surface temperature are new. The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen and Ross sea sectors. The composite fields reveal anomalies that are organized in distinct large-scale coherent patterns with opposing polarities during the extremes of SOI, and suggest a seesaw pattern of climate anomalies associated with the SO. The positive (negative) phases of the SOI are associated with generally lower (higher) sea-level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are clearly evident. These results can be used to explain recent anomalies in the sea ice cover associated with the SOI: the record decrease in the sea ice extent in the Bellingshausen Sea from mid-1988 through early 1991; the relationship between Ross Sea SST and ENSO signal, and reduced sea ice concentration in the Ross Sea; and, the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea, and the lengthening of the ice season in the western Ross Sea, Bellinghausen Sea and central Weddell Sea gyre over the period 1988-1994. Four ENSO episodes over the last 17 years contributed to a negative bias in the mean of the SOI (-0.5). Physical mechanisms by which the anomalies are linked to extrapolar climate are not discussed here.