Ocean response to mesoscale atmospheric forcing

Abstract

Many processes have been proposed as possible forcing mechanisms for mesoscale oceanic variability. The present study shows that atmospheric forcing can be an important source of mesoscale variability in the ocean. We show that the response is linearly proportional to the product of the time scale of the storm and its intensity. We clarify the point that for storms with scales considerably smaller than the barotropic Rossby radius of deformation, the oceanic stratification and the horizontal extent of the storm are the only factors determining the penetration depth of the response, implying that it is not the Rossby radius of deformation but rather the scale of penetration depth (h = (f/N)L) that characterizes the response.

In exploring the effect of differing eddy-viscosity parametization on oceanic response, we find no significant qualitative differences, although as one might expect we find quantitative differences in the results.

The role of the mixed layer is considered very important in the transfer of surface stresses down into the system. The mixed layer does not seem to be important in determining the characteristic lengths of the problem, however, at least for storms that give a penetration depth considerably larger than the mixed layer (for a mixed layer on the order of 20 m, the storm should be larger than a few kilometers).

The non-linear advection terms seem to affect the adjustment process more by reducing the associated wave energy than by modifying the characteristics of the geostrophic response. Finally, making the stratification more realistic has no significant impact on the resulting oceanic response.