8.6 The Characteristic Variability and Connection to the Underlying Synoptic Activity of the Amundsen-Bellingshausen Seas Low

Wednesday, 9 January 2013: 9:45 AM
Ballroom B (Austin Convention Center)
Alex J. Wovrosh, The Ohio State University, Athens, OH; and R. L. Fogt, R. A. Langen, and I. Simmonds

Recent studies have noted an asymmetrical climate change across Antarctica, with significant warming in West Antarctica and the Antarctica Peninsula, and primarily insignificant trends in East Antarctica. Due to its proximity, variations in the position and intensity of the Amundsen-Bellingshausen Seas Low (ABSL) are a suspected atmospheric mechanism. Here, we investigate the ABSL to understand its characteristic variability and underlying synoptic-scale influences, based on three reanalysis datasets. The ABSL is defined as the minimum monthly pressure in the 45° – 75°S, 180° – 60°W domain. Using this criterion, a significant north-south and east-west progression is noted in the climatological (1979-2001 average) ABSL, which is strongly tied to the location of the maximum cyclone system density and minimum cyclone central pressures. More than 550 cyclones a year were identified in the vicinity of the ABSL; during spring, significant trends in their central pressures are noted in the Ross Sea. The implied changes in temperature advection by these stronger systems are consistent with the warming in West Antarctica. The strongest cyclone events (i.e., the ten with the deepest central pressures) also demonstrate a connection to the climatological ABSL, albeit weaker. Moreover, these strong cyclone events are significantly linked to the Southern Annular Mode (SAM), particularly in their annual frequency and location/steering in the summer. This shows that large-scale forcing, such as from the SAM, may influence the strongest cyclones in the region and could allow for the prediction of such events.
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