Cooperative Institute for Research in Environmental Sciences

Atmospheric impacts of an Arctic sea ice minimum as seen in the Community Atmosphere Model

Cassano, E.N., J.J. Cassano, M.E. Higgins, and M.C. Serreze

2014, International Journal of Climatology, 34, Issue 3, 766-779, DOI: 10.1002/joc.3723.

There is growing recognition that reductions in Arctic sea ice extent will influence patterns of atmospheric circulation both within and beyond the Arctic. September 2007 had the second lowest Arctic sea ice extent recorded in the satellite era. We explore the impact of 2007 ice conditions on atmospheric circulation and surface temperatures and fluxes through a series of model experiments with the NCAR Community Atmospheric Model version 3 (CAM3). 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 during autumn and winter with lower sea level pressure (SLP) and tropospheric pressure simulated over much of the Arctic for the 2007 sea ice experiment. The atmospheric response to 2007 ice conditions was much weaker during summer than autumn and winter, with negative anomalies in SLP simulated from Alaska across the Arctic to Greenland. Higher temperatures and larger surface fluxes to the atmosphere in the western Arctic and over the Barents and Kara Seas were also simulated. Results from the CAM3 experiments were compared to observed SLP anomalies from the NCEP/NCAR Reanalysis data. The observed SLP anomalies during spring are nearly opposite to those simulated in the CAM3 experiment, as well as large differences between observed SLP and simulated SLP differences in the CAM3 experiments during JJA, suggesting that the sea ice conditions preceding and during the summer of 2007 were not responsible for creating an atmospheric circulation pattern which favored the large observed sea ice loss. The simulated and observed atmospheric circulation anomalies during the autumn and winter were more similar with the exception of a strong high pressure system in the Beaufort Sea which was not simulated, suggesting that the forced atmospheric response to reduced sea ice was in part responsible for the observed atmospheric circulation anomalies during those seasons.