Summer retreat of Arctic sea ice: Role of summer winds

Abstract

The unprecedented retreat of first‐year ice during summer 2007 was enhanced by strong poleward drift over the western Arctic induced by anomalously high sea‐level pressure (SLP) over the Beaufort Sea that persisted throughout much of the summer. Comparison of the tracks of drifting buoys with monthly mean SLP charts shows a substantial Ekman drift. By means of linear regression analysis it is shown that Ekman drift during summer has played an important role in regulating annual minimum Arctic sea‐ice extent in prior years as well. In combination, the preconditioning by events in prior years, as represented by an index of May multi‐year ice, and current atmospheric conditions, as represented by an index of July–August–September SLP anomalies over the Arctic basin account for ∼60% of the year‐to‐year variance of September sea‐ice extent since 1979.