Sea ice-air interactions amplify multidecadal variability in the North Atlantic and Arctic region

Abstract

Winter surface air temperature (Tas) over the Barents-Kara Seas (BKS) and other Arctic regions has experienced rapid warming since the late 1990 that has been linked to the concurring cooling over Eurasia1-3. However, the cause of this accelerated BKS warming is not well understood, and whether and how internal variability may have contributed to this warming is unclear. Through analyses of observations and model simulations, we show that two-way interactions between sea ice and air amplify multidecadal variability in Arctic sea-ice cover (SIC) and sea surface temperatures (SST) from the North Atlantic to BKS, and produce large multidecadal variations in Tas over the BKS, Greenland-Norwegian Seas and Baffin Bay. Advection of SST anomalies from the North Atlantic to the Arctic causes SIC to change, which produces large anomalies in surface energy fluxes and Tas. However, the sea ice-air interactions also amplify the variations in SIC and SST, and the Atlantic Meridional Overturning Circulation (AMOC) mainly through local surface fluxes. When sea ice is fixed or melts away under increasing CO2, not only Arctic Tas multidecadal variations disappear, but also the SIC, SST and AMOC variations are greatly reduced. The results suggest that sea ice-air interactions are vital for multidecadal climate variability not only in the Arctic but also in the North Atlantic, similar to air-sea interactions for tropical climate. As Arctic sea ice is projected to melt away4,5, these interactions and thus multidecadal variability from the North Atlantic to the Arctic will likely weaken in the coming decades.