Response of European Temperature Extremes to a Weakened AMOC

The projected weakening of the Atlantic Meridional Overturning Circulation (AMOC) poses substantial risks for global and regional climate stability. While the large-scale cooling associated with a weakened AMOC is well-documented, how weather and climate extremes respond to such changes remains little examined. Here, we investigate how recent European summer and winter temperature extremes (2018-2022) would change under different weakened AMOC states using the Alfred Wegener Institute Climate Model (AWI-CM3). We generate three sets of five-member ensemble simulations, each representing a different AMOC state: a factual (present-day AMOC) state and two counterfactual states with a weakened and a shut-down AMOC. All simulations are spectrally nudged to the large-scale winds observed during 2017-2022. We thus focus primarily on the thermodynamic impacts induced by AMOC weakening within the same realization of atmospheric variability. Our research indicates that a weakened AMOC generally reduces the occurrence of summer hot days, though this response is spatially heterogeneous, implying a flow-dependence of the AMOC-related impact. For instance, Eastern Europe remains comparatively less affected even when AMOC strength is reduced by 60% relative to the present day conditions. In contrast, winter cold extremes are substantially intensified. We observe a drastic increase in cold days, with daily minimum temperatures during these events decreasing by more than 6 °C in several northwestern European capital cities. These findings highlight the nonlinear and seasonally asymmetric responses of European temperature extremes to AMOC weakening and provide important insights for regional climate risk assessment and adaptation strategies.