Characteristics of the broadscale antarctic sea ice extent and the associated atmospheric circulation 1972–1977

Abstract

The monthly and seasonal means, extremes and variability of the Southern Hemisphere sea ice are examined for a five year period. Its variability is found to be greatest in the longitudes of the Antarctic coastal embayments, and a small but general decline in extent at all seasons throughout the period is observed. At near maximum ice extent (July to November), the 5 year mean of the zonal westerlies to the north of the ice increases with increasing ice extent; however for individual years, at maximum ice extent, there is no clear correlation between zonally averaged ice extent and the strength of the zonal westerlies in the preceding or succeeding month. Comparison with the 5 year mean longitudinal pattern of atmospheric pressure maxima and minima at the latitude of the Antarctic trough points generally to asymmetries in the ice edge, such that it is further north and more variable in regions of frequent low pressure, and further south in regions of relatively high pressure. Examination of a specific longitudinal zone indicates that the pattern of ice extent is clearly regional, and apparently related to variations in the combined oceanic and atmospheric circulation particularly in the Antarctic embayments.