Parameterization of Eddy Effects on Mixed Layers and Tracer Transport: A Linearized Eddy Perspective

摘要

Two aspects of the effects of eddies on ocean circulation have proven difficult to parameterize: eddy effects in regions of neutrally stable (or convecting) fluid and the mixing of passive tracers. The effects of linearized eddies, although a restrictive parameter regime, can be straightforwardly computed in these cases. The eddy effects in areas of neutral stability—for example, mixed layers—blend naturally into those in the stably stratified water below, although losing the concept of bolus velocity. Instead, the mixed layer density is advected by an extra overturning velocity and is diffused laterally by a diffusion that is the same as the eddy diffusion at the top of the stably stratified fluid. Passive tracers are advected by the bolus velocity and mixed by the same diffusivity as is used to compute the bolus velocity at that location, so that two different diffusivities are not needed.