Parameterization of Eddy Fluxes near Oceanic Boundaries

In the stably stratified interior of the ocean, mesoscale eddies transport materials by quasiadiabatic isopycnal stirring. Resolving or parameterizing these effects is important for modeling the oceanic general circulation and climate. Near the bottom and near the surface, however, microscale boundary-layer turbulence overcomes the adiabatic, isopycnal constraints for the mesoscale transport. In this paper we present a formalism for representing this transition from adiabatic, isopycnally-oriented mesoscale fluxes in the interior to the diabatic, along-boundary mesoscale fluxes near the boundaries. We propose a simple parameterization form and illustrate its consequences in an idealized flow. We emphasize that the transition is not confined to the turbulent boundary layers, but extends into the partially diabatic transition layers on their interiorward edge. A transition layer occurs because of the mesoscale variability in the boundary layer and the associated mesoscale-microscale dynamical coupling.