Adiabatic Processes Contribute to the Rapid Warming of Subpolar North Atlantic During 1993–2010

Abstract

AbstractThe Subpolar North Atlantic (SPNA) is a region with complex dynamics, and governs the global heat transport by regulating the Atlantic Meridional Overturning Circulation. During 1993–2010, the upper ocean of SPNA has rapidly warmed. Most studies to date focused on the diabatic processes and meridional heat transport leading to this rapid warming, neglecting the role of adiabatic processes and associated heat redistribution. Here, we investigate the ability of adiabatic Rossby wave adjustment to produce this warming event by designed numerical experiments with a set of simple models, including one‐layer model, reduced‐gravity model and two‐layer model. The comparison between these numerical simulations with observations demonstrates that this rapid warming in the western SPNA is partly generated by the wind stress anomalies. The wind stress curl anomalies in the central and eastern of SPNA trigger the topographic and planetary Rossby waves, propagating the downwelling signals along their waveguides to redistribute heat in the upper ocean and warm the Labrador Sea and Irminger Sea with a 4‐ or 7‐year time lag. Hence, the baroclinic mode dominates the magnitude of the adiabatic warming in the SPNA and the topography shapes its spatial pattern. In addition, local and remote wind forcing jointly contributes to this warming.