5.4
Arctic sea ice retreats in 2007 and 2008 follow thinning trend
Ron Lindsay, University of Washington, Seattle, WA; and A. Schweiger, J. Zhang, M. Steele, and H. Stern
The minimum of Arctic sea ice extent in the summer of 2007 was unprecedented in the previous historical record and the extent in 2008 was nearly as low. A coupled ice–ocean model is used to determine the state of the ice and ocean over the past 30 yr to investigate the causes of this ice extent minimum within a historical perspective. It is found that even though the 2007 ice extent was strongly anomalous, the loss in total ice mass was not. Rather, the 2007 ice mass loss is largely consistent with a steady decrease in ice thickness that began in 1987. Since then, the simulated mean September ice thickness within the Arctic Ocean has declined from 3.7 to 2.6 m at a rate of 0.57 m/decade. Both the area coverage of thin ice at the beginning of the melt season and the total volume of ice lost in the summer have been steadily increasing. The combined impact of these two trends caused a large reduction in the September mean ice concentration in the Arctic Ocean. This created conditions during the summer of 2007 that allowed persistent winds to push the remaining ice from the Pacific side to the Atlantic side of the basin and more than usual into the Greenland Sea. Large areas of open water were exposed, resulting in the record ice extent anomaly. The very thin ice that was present at the beginning of 2008 allowed a similar large reduction in the ice concentration but the lack of persistent anomalous winds precluded the development of another record low ice extent.
Session 5, Rapid Polar Environmental Change
Tuesday, 19 May 2009, 8:30 AM-9:30 AM, Capitol Ballroom AB
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