Basinwide response of the Atlantic Meridional Overturning Circulation to interannual wind forcing

Abstract:

An eddy-resolving OGCM (Ocean circulation model for the Earth simulator/OFES) and a simple wind-driven two-layer model are used to investigate the role of momentum fluxes in driving the AMOC variability throughout the Atlantic basin from 1950-2010. Diagnostic analysis using the OFES suggests that interior baroclinic Rossby waves and coastal topographic waves play essential roles in modulating the AMOC interannual variability. The proposed mechanisms are evaluated in the context of the two-layer model. High-latitude anomalies are communicated to lower latitudes by topographic waves and account for about 50% of the AMOC interannual variability in the subtropics. The topographic waves and the large scale Rossby waves excited by wind forcing set up coherent AMOC interannual variability patterns across the tropics and subtropics. The comparison between the simple model and OGCM results suggest that a large fraction of the AMOC interannual variability in the OGCM can be explained by wind-driven dynamics.