Evaluating the contribution of Asian Aerosol Emissions to the North Atlantic Warming Hole

Over the past century, the sea surface temperature (SST) in the subpolar North Atlantic (SPNA) has decreased, resulting in the North Atlantic warming hole. While anthropogenic aerosols (AAs) have been linked to this phenomenon, the specific role of remote Asian AAs remains unclear. Using an ensemble of fully coupled experiments with idealized radiative forcing, we reveal a two-stage response of upper ocean temperature in the SPNA to increased Asian AAs. The initial, fast response is characterized by anomalous warming in the northern SPNA, delaying the warming hole. This fast warming arises from the suppression of turbulent heat flux losses driven by anomalous easterly winds, with mean ocean circulation and downwelling Rossby waves contributing to its westward propagation. On longer timescales, the initial warming transitions into a widespread cooling across the SPNA, resembling the observed warming hole. This cooling is primarily driven by a reduction in northward heat transport due to a weakening of the Atlantic Meridional Overturning Circulation, as well as the anomalous southward transport of Labrador cold water. The two-stage modulation of NAWH by Asian AAs is supported by models with different configurations. Our findings suggest that regional AA emissions may play a non-negligible role in modulating air-sea interactions over the North Atlantic, serving as one contributing factor to the evolution of the warming hole.