Abstract

This study examines the emergence and evolution of a mesoscale sea surface temperature (SST) variability induced by a uniform and impulsive wind stress when an embedding quasigeostrophic (QG) flow is present. The SST variability which is triggered by the mixed-layer deepening closely resembles some characteristic properties of the QG flow, namely either the subsurface temperature or relative vorticity, depending on the amplitude of the deepening. The SST variance can have the same order of magnitude as the subsurface temperature variance. Within 10 days, the SST field, which is stirred only by the horizontal QG flow, displays a rapid spectral evolution characterized by the emergence of small-scale structures and the appearance of thermal fronts located in the QG jet areas. This evolution depends only on the deformation of the large-scale structures of the SST field, initially resulting from the mixed-layer deepening, by the QG strain field. In contrast with SST, later evolution of the mixed-layer depth is characterized by the emergence of large-scale structures. From these dynamical results, it is speculated that, when nonuniform initial conditions are considered, the resulting SST spatial variability should be more closely related to the subsurface temperature and the SST variance could be significantly increased.

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