Numerical Simulations of the Equilibrium between Eddy-Induced Restratification and Vertical Mixing

摘要

Submesoscale dynamics are hypothesized to play a leading-order role in setting the stratification of the mixed layer via the interaction of submesoscale eddies and surface forcing. Previous studies of such interactions have generally focused on the time-evolving characteristics of submesoscale turbulence, such as the spindown of a baroclinically unstable front. This paper focuses instead on the equilibrium dynamics of the oceanic mixed layer, where forcing and dissipation are in balance, through a combination of scaling analysis and numerical simulations. The steady dynamics are well described by a turbulent thermal wind balance, with external forcing parameterized by a strong vertical diffusivity kappa. Scaling laws are developed for the characteristic vertical length scale L-upsilon, ageostrophic velocity scales U and V, buoyancy frequency N-2, and eddy buoyancy flux