Antarctic Peninsula mesoscale cyclone variability and climatic impacts influenced by the SAM

The frequency of mesoscale cyclones in the Western Antarctic Peninsula (WAP) region during 1991-94 is correlated with the Southern Hemisphere Annular Mode (SAM) index, most strongly during winter and spring. Also, during periods of positive SAM index polarity there is a shift in the storm tracks to favor more east-bound trajectories, consistent with strengthening of circumpolar westerlies. The presence of mesoscale cyclones is associated with positive near-surface-air temperature anomalies in the WAP region year-round, largest during winter.