Frequency of winter temperature extremes over northern Eurasia dominated by AMOC

Abstract Widespread observed and projected increases in warm extremes, along with decreases in cold extremes, have been confirmed to be consistent with global and regional warming. However, in our study, decadal variations in surface air temperature (SAT) extremes over northern Eurasia in winter are primarily dominated by the Atlantic Meridional Overturning Circulation (AMOC), rather than an anthropogenically forcing. Based on reanalysis and state-of-the-art model simulations, we highlight that the decadal weakening of AMOC narrowed the generalized extreme value (GEV) distribution of winter SAT via diminishing its variance, and thus inducing fewer SAT extremes. On the contrary, the decadal enhancing of AMOC corresponded to the increase in the SAT variance over northern Eurasia, making a milder GEV distribution and generating more warm and cold extremes. These AMOC induced variations in SAT extremes may depend on the ocean heat transported into the atmosphere for air motion over northern Eurasia and the Arctic amplification caused by the heat advection from the northward-flowing Atlantic water.