Subpolar North Atlantic cooling forced by increased storminess

A well-known exception to rising sea surface temperatures (SST) across the globe is the subpolar North Atlantic, where SST has been declining at a rate of 0.39 (±0.23) K/century. While it has been suggested that this cold blob results from an Atlantic Meridional Overturning Circulation (AMOC) slowdown, observation-based evidence presented here indicates that increased storminess can instead account for the cooling trend. Specifically, a 100-year SST trend simulated by a one-dimensional idealized ocean model forced with observed air-sea heat fluxes over the cold blob region explains 87% of the observed cooling trend. The simulations suggest that 51% of the observed cooling trend results directly from the increased heat loss from the ocean surface; while the remaining 36% is due to an increase in deep convection in the area, an indirect effect of the heat loss. A northward migration of the jet stream that exposes the subpolar North Atlantic to intensified storminess is believed responsible for the heat loss from the ocean.