A critical role of extreme Atlantic windstorms in Arctic warming

Abstract

Here we show that Atlantic windstorms of extreme category in northern winter tend to follow a well-defined route toward the Atlantic sector of Arctic, and that heat and moisture transported by these extreme storms significantly warm the Arctic. A positive North Atlantic Oscillation condition and the associated intensified upper-level Atlantic jet provide favorable conditions for those extreme storm developments through enhanced vertical wind shear. These extreme windstorms lead to two discernible impacts on the Arctic: 1) enhanced poleward energy transport by moisture intrusion to the Arctic, which accompanies increased longwave downward radiation and 2) the occurrence of blocking-like patterns after the storm break-up. During these periods, significant Arctic warming was observed of a 10-fold increase versus normal and weak storms. The poleward deflections of extreme storms, and the Arctic warming driven by such storms, are well simulated in numerical experiments with oceanatmosphere coupled models.