Antarctic Peninsula climate variability and its causes as revealed by analysis of instrumental records

Climate observations made since the mid twentieth century reveal that the Antarctic Peninsula is a region of extreme climate variability and change. The pattern of change is, however, both seasonally and spatially inhomogeneous. Limited data from the east (Weddell Sea) coast indicate that surface air temperatures here are rising at around 0.03 degreesC per year in all seasons. On the west (Bellingshausen Sea) coast, summer temperature trends are similar to those prevailing on the east coast but, in winter, warming trends of over 0.1 degreesC per year are observed, making this the most rapidly warming part of the Southern Hemisphere. Rapid warming is confined to the very lowest levels of the atmosphere and warming of the free troposphere over the Peninsula is not statistically significantly different from the Southern Hemisphere average. Interannual variations in winter temperatures on the west coast are strongly correlated with variations in atmospheric circulation and sea ice extent, suggesting that both atmospheric and ice/ocean processes may be contributing to the long-term warming. However, there is little observational evidence to support long-term atmospheric circulation changes. Coupled atmosphere-ocean general circulation model (AOGCM) experiments, forced with observed greenhouse gas increase, fail to reproduce the observed pattern of warming around the Peninsula. However, current AOGCMs may not be sophisticated enough or of high enough resolution to represent all of the processes that control climate on a regional scale around the Antarctic Peninsula.