Toward an Energetically Consistent, Resolution Aware Parameterization of Ocean Mesoscale Eddies

Abstract

A subgrid-scale eddy parameterization is developed, which makes use of an explicit eddy kinetic energy budget and can be applied at both “non-eddying” and “eddy-permitting” resolutions. The subgrid-scale eddies exchange energy with the resolved flow in both directions via a parameterization of baroclinic instability (based on the established formulation of Gent and McWilliams) and biharmonic and negative Laplacian viscosity terms. This formulation represents the turbulent cascades of energy and enstrophy consistent with our current understanding of the turbulent eddy energy cycle. At the same time, the approach is simple and general enough to be readily implemented in ocean climate models, without adding significant computational cost. The closure has been implemented in the Modular Ocean Model Version 6 and tested in the “Neverworld” configuration, which employs an idealized analytically defined topography designed as a testbed for mesoscale eddy parameterizations. The parameterization performs well over a range of resolutions, seamlessly connecting non-eddying and eddy-resolving regimes.