Abstract
Wind forcing has been widely recognized as an important driver of submesoscale motions associated with mesoscale eddies or ocean fronts by down-front wind. Here, we show that the wind influence can also trigger submesoscale motions by altering the vertical structure of a mesoscale eddy. Using high-resolution idealized simulations, the result reveal that wind forcing firstly induces a pronounced vertical tilt (~70 km) of an anticyclonic eddy via Ekman induced advection of geostrophic vorticity in theory of Stern (1965). Then, this wind-induced tilting follows a clear dynamical pathway toward submesoscale development. The tilted anticyclone first develops a wavenumber-1 vortex Rossby wave (VRW) during the early stage. Subsequent deformation and breakdown of the VRW generate small-scale filaments and fronts along the eddy periphery, accompanied by enhanced strain and frontogenesis. As a result of the effect of down-front winds and the modified potential vorticity structure, mixed barotropic–baroclinic instability and symmetric instability develop, leading to vigorous submesoscale motions. Energy conversion diagnostics further show that baroclinic conversion dominates the submesoscale energy supply through the release of mesoscale available potential energy (APE), whereas barotropic conversion and geostrophic shear production make substantially smaller contributions. These findings identify wind-induced eddy tilting as an another importantly dynamical pathway to promote submesoscale motions.

 

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