The Influence of Arctic Clouds on SST in CESM2

As sea ice cover declines in the Arctic, open ocean extends over more area and is exposed earlier in the year. Previous work has found that the timing of when sea ice completely melts can influence ocean heat uptake and fall SST. Earlier ice retreat is linked to increased energy input into the open ocean in part because of the strong seasonal cycles of radiative fluxes in the Arctic. Clouds in the Arctic are an important control on the radiative fluxes, surface energy balance and presumably ocean heat budget. However, the net effect of clouds – warming or cooling the surface – strongly depends on the time of year. In this work we ask if clouds can in fact influence SST in the Community Earth System Model version 2 by modulating the surface energy balance. Analysis of the surface energy balance and ocean heat budget reveals that clouds can influence ocean temperatures, predominately by cooling the surface. Using experiments with variable carbon dioxide concentrations, we find that the connection between clouds and fall SST has increased as the Arctic warms and sea ice declines. These results suggest clouds may play a larger role for ocean temperatures in the future.