Vertical Mixing and Transports through a Stratified Shear Layer

Abstract

A stratified shear layer was generated in the laboratory by driving a turbulent mixed layer of depth D over a quiescent, deep dense layer. As a result, a density interface of thickness δb across which the buoyancy jump is ?b was formed between the upper and lower layers. This density interface was embedded in a velocity shear layer of thickness δs across which the velocity jump was ?U. Detailed velocity, density, and average local Richardson number (Rig) measurements were made through the stratified shear layer, from which the fluxes of momentum and density through the interface as well as energetics of the stratified shear layer were evaluated as a function of Rig. The quantities measured included the flux Richardson number (Rif), the dissipation flux coefficient (Γ), and the eddy diffusivities of momentum and density (Km and K?), averaged across the shear layer. The results were compared with various deep and coastal oceanic data as well as common oceanic eddy diffusivity and flux parameterization schemes.