Amplified European future warming under mesoscale-resolving sea surface temperature forcing

Ocean mesoscale sea surface temperature (SST) variability associated with eddies, fronts, and filaments strongly modulates air–sea heat and moisture exchanges, yet its role in shaping future regional climate change remains poorly constrained. This uncertainty largely stems from the fact that most global climate models do not resolve the ocean mesoscale. Here, we assess how the SST mesoscale influences the North Atlantic–European climate under present-day and future warming conditions. We use a high-resolution (~16 km) global atmospheric model forced with SSTs from an eddy-rich coupled model, comparing simulations with fully resolved mesoscale SSTs to experiments in which these have been spatially smoothed. While the atmospheric mean state shows only minor sensitivity to mesoscale SSTs under present-day conditions, under future climate conditions, mesoscale SST anomalies contribute to amplifying European winter climate change. Enhanced latent heat release along the Gulf Stream associated with mesoscale SST anomalies increases baroclinic instability, intensifies the North Atlantic storm track, and drives a circulation response resembling a positive phase of the North Atlantic Oscillation. This results in substantially warmer and wetter European winters. In contrast, suppressing mesoscale SST variability weakens storm activity, favors atmospheric blockings, and strongly reduces projected warming. Our results demonstrate that the ocean mesoscale exerts a first-order control on the response of the mid-latitude atmospheric circulation to climate warming, and suggest that climate projections based on standard resolution models may systematically underestimate regional climate change over Europe. Resolving mesoscale ocean–atmosphere interactions emerges as a key requirement for  more reliable future climate projections.