North Atlantic Ocean response to future anthropogenic forcing in a coupled general ciruclation model

Aiguo Dai, G.A. Meehl, W.M. Washington, and W.G. Strand National Center for Atmospheric Research, Boulder, CO

Abstract:

The Parallel Climate Model (PCM), a coupled general circulaiton model without flux adjustments, was used to simulate (using ensemble runs) the climate response to observation-based (for the 20th century) and projected (for the 21st and 22nd centuries) greenhouse gas and sulfate aerosol forcing. In this study, we focus on the changes in the North Atlantic Ocean circulation. We found that the overturning circulaiton and poleward volume and heat transports decrease by ~18% from the 1961-1990 to 2070-2099 and by ~30% by the end of the 22nd century. This change is mainly due to the thermal effect of surface warming on water density around Iceland. Furthermore, we found that the North Atlantic Drift current extends eastward, resulting in a cooling in the midlatitude central North Atlantic (extending to >1km depth). Our results suggest that changes in ocean circulations could modulate regional climate response to future greenhouse gas forcing.