Atmospheric circulation response to 2007 sea ice extent
Elizabeth N. Cassano, CIRES/Univ. of Colorado, Boulder, CO; and J. J. Cassano and M. E. Higgins
Sea ice extent in the Arctic during the summer and early autumn of 2007 was unprecedented during the satellite era, with a record minimum sea ice extent observed in September 2007. The impact of this anomalous sea ice extent on atmospheric circulation was explored through a series of model experiments with the NCAR Community Atmospheric Model (CAM). Two 30-year simulations were performed, one using climatological sea ice extent for the end of the 20th century and a second using the observed sea ice extent from 2007. Circulation differences over the Northern Hemisphere were most prominent in the autumn (SON) and winter (DJF) with lower sea level pressure (SLP) and 500 and 300 mb geopotential heights simulated over the much of the Arctic for the 2007 sea ice experiment. The atmospheric response to the 2007 sea ice was much weaker during summer (JJA), with low sea level pressure anomalies simulated from Alaska across the Arctic to Greenland.
The results of the CAM experiments were compared to SLP anomalies from the NCEP/NCAR reanalysis for 2007. The observed SLP anomalies during spring (MAM) and JJA were nearly opposite those simulated in the CAM 2007 sea ice experiment which suggests that the sea ice conditions preceding and during the summer of 2007 were not responsible for creating an anomalous atmospheric circulation pattern which favored the large observed sea ice loss. The simulated and observed atmospheric circulation anomalies during the autumn and winter were much more similar, suggesting that the forced atmospheric response to reduced sea ice was in part responsible for the observed atmospheric circulation anomalies during the fall and winter of 2007.
Session 16, Atmosphere-Ocean-Sea Ice Interactions
Thursday, 21 May 2009, 10:30 AM-12:30 PM, Capitol Ballroom AB
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