ACCESS-OM-02 model simulations of the 2023 extreme North Atlantic marine heat wave
Matthew England
During 2023 an unprecedented and near basin-scale marine heatwave developed in the North Atlantic during summer, peaking in July. The warming spread across virtually all regions of the North Atlantic, including the subpolar ocean where a cooling trend over the past 50-100 years has been linked to a slowdown in the Atlantic Meridional Overturning Circulation (AMOC). Yet the mechanisms that led to this exceptional surface ocean warming remain unclear. Here we use observationally-constrained atmospheric reanalyses alongside ocean observations and ACCESS-OM-02 model simulations to unravel the drivers of the record North Atlantic warming, finding a combination of preconditioned warming, weak winds, strongly shoaling mixed layers, and clearer than average skies combined to drive a rapid buildup of heat in a shallow surface layer of the North Atlantic. The implications of these findings will be discussed, including what the models do well, and not so well, in capturing this extreme warming event.
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