Upper-Ocean Response to Strong Wind Forcing in a Loop Current Eddy

Abstract From autumn to spring, the dynamics and thermodynamics of the anticyclonic eddies detached from the Loop Current in the Gulf of Mexico are actively influenced by the passage of cold fronts and accompanying strong northerly winds (locally called Nortes). In this work, the dynamical mechanisms of eddy–strong wind interactions are analyzed based on realistic, forced, eddy-permitting (∼3 km) numerical simulations of the NEMO ocean model that reproduce observations collected from an oceanographic cruise in November 2022 and satellite data. We focus the analysis on three interconnected aspects: (i) the upper-ocean rapid response to the passage of Norte events, where deepening of the mixed layer and upwelling velocities in the eddy interior are identified; (ii) the modulation of the vertical velocity patterns by the wind stress curl and the horizontal advection of vorticity due to Ekman transport, finding that the latter term is the dominant contributor under moderate winds, and similar contributions from both terms under strong wind forcing; and (iii) the rate of wind work and wind power input on the geostrophic flow over the anticyclone and its dependence on specific vortex and wind parameters. By contrasting simulations that use the absolute or relative wind in the wind stress parameterization, we also find that the eddy is either intensified or less damped in the absolute wind simulation. Furthermore, this is a dynamically consistent response identifiable in day-to-day variations. This analysis contributes to the understanding of key air–sea interactions occurring at the mesoscale in a highly energetic ocean region.