Southern Ocean Surface Climate Trends Since 1979: Context and Comparison with Earlier Decades

This study compares the distribution of surface climate trends over the Southern Ocean for two time periods, 1979-2010 and 1957-1978, using a wide variety of data sets including un-interpolated marine archives, station data, Reanalysis and satellite instruments. Apart from the region including the Antarctic Peninsula and adjacent areas of West Antarctica, sea surface temperatures (SSTs) and surface air temperatures have decreased since 1979, consistent with the observed increase in Antarctic sea ice. In contrast, the earlier period shows a warming of Southern Ocean SSTs, a pattern verified by air temperatures from station data. The distribution of trends in marine cloudiness, sea level pressure (SLP), and zonal wind provide additional evidence for distinct trends in the two periods. In the early period, positive SST trends are accompanied by positive trends in SLP, negative trends in surface westerly winds and cloud cover. In the later period, these trends are reversed in sign. Such physically-consistent trends across a range of independently-measured climate parameters provide a broader context for the recent increase in Antarctic sea ice.