Midlatitude Mesoscale Thermal Air-sea Interaction Enhanced by Greenhouse Warming

Abstract The influence of greenhouse warming on mesoscale air-sea interactions, crucial for modulating ocean circulation and climate variability, remains largely unexplored due to the limited resolution of current climate models. This study addresses this gap by analyzing eddy-resolving high-resolution climate simulations and observations, focusing on the coupling between mesoscale sea surface temperature (SST) and latent heat flux (LHF) in winter. Our findings reveal a consistent increase in mesoscale SST-LHF coupling in the major western boundary current regions under warming, characterized by a heightened nonlinearity between warm and cold eddies and a more pronounced enhancement in the northern hemisphere. To understand the dynamics, we develop a theoretical framework that links mesoscale thermal coupling changes to large-scale factors, which indicates that the projected changes are collectively determined by historical background wind, SST, and the rate of SST warming. Among these factors, the large-scale SST and its warming rate are the primary drivers of hemispheric asymmetry in mesoscale coupling intensification. This study introduces a simplified approach for assessing the projected mesoscale thermal coupling changes and implies a growing significance of mesoscale air-sea interaction in shaping weather and climate patterns in a warming world.