92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Monday, 23 January 2012: 5:15 PM
The Weather-Climate Interface of the Amundsen-Bellingshausen Seas Low
Room 354 (New Orleans Convention Center )
C. Virgei, Ohio University, Athens, OH; and R. L. Fogt, A. J. Wovrosh, and R. A. Langen

Recent advances in Antarctic climate have led to a better understanding of the synoptic variability of the Southern Ocean. Studies have also noted dramatic warming throughout West Antarctica and on the Antarctic Peninsula. This talk connects these activities by linking variations of the Amundsen Bellingshausen Seas Low (ABSL) with the underlying synoptic variability. The ABSL has a well-known seasonal cycle in terms of location and central pressure, however we also note significant interplay among the intensity and location of the ABSL beyond the seasonal cycle. Using the University of Melbourne's automated cyclone tracking scheme, cyclone characteristics in the vicinity of the ABSL [45 -75S, 180 - 60W] are analyzed using the NNR, ERA-40, and JRA-25 atmospheric reanalysis data sets during the years 1979 - 2001. We note that many of these significant relationships of the climatological low result from variations in the location, intensity, and number of individual cyclone events. Of particular interest are the top ten strongest cyclone events, as these events most dramatically impact the regional climate (i.e., temperature, sea ice, precipitation) and influence the climatological ABSL. Through statistical tests, these top ten cyclones were then compared to the climatological mean pressure (i.e., the ABSL), unveiling significant differences that highlight anomalous conditions across the midlatitudes and throughout the region which give rise to these intense cyclones. Importantly, in many cases the difference field resembles a positive Southern Annular Mode (SAM) pattern, indicating that the anomalous high pressure through the mid latitudes may actually influence the track of these top ten cyclones. It is thus evident that the observed climate changes in the region are induced primarily from strong individual cyclones, which themselves are strongly influenced by the large-scale climate.

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