Thursday, 13 January 2005
Investigating the Relationship Between Modeled Ice Extent and the AO/NAO
Recent observational studies have identified a strong relationship between positive phases of the AO/NAO mode in winter and minimum summertime Arctic sea ice extents. From about 1989-1995 there was a period of positive AO unprecedented in the past 50 years, setting up an Arctic circulation with a stronger Transpolar Drift and Fram Strait export. It has been postulated that the prolonged existence of the positive AO managed to flush much of the thicker multiyear pack ice from the Arctic, leaving the central basin with a larger fraction of thinner firstyear ice than typical. Recent years have seen the winter AO relax to a more neutral state. Yet 2002 and 2003 have seen extreme summer ice losses. These are argued as a delayed response to the sea ice thinning. It appears that 2004 may be another very low year. We investigate this hypothesis using a dynamic-thermodynamic sea ice model which explicitly tracks ice age, and attempt to define relations between the AO and the Multiyear Ice Extent in the Arctic.
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