Cooling effect of mesoscale SST perturbations induced rotational wind in the Kuroshio Extension

Abstract

Mesoscale SST perturbations induced wind stress field perturbations have feedback effect on the ocean through influencing air-sea heat and momentum fluxes. Unlike the thermal feedback mechanism that is well understood, momentum feedback still needs to be studied, especially about the respective roles of divergent and rotational wind components. In this study, momentum feedback was examined using an ocean model and an empirical equation, which solved wind stress field perturbations from their divergence and curl that were estimated from time-evolving downwind and crosswind SST gradients. Through several numerical experiments, it was found that the divergent wind can induce positive and negative SST changes at varying regions and depths. On the contrary, the rotational wind can cool the upper ocean and reduce SST by 0.1°C on average.