Energetically Consistent, Resolution Aware, Parameterization of Mesoscale Eddies in the Ocean

This presentation discusses the formulation of subgrid-scale eddy parameterizations, which make use of an explicit eddy kinetic energy (EKE) budget. Subgrid-scale eddies can extract energy from the resolved flow via baroclinic instability (parameterized based on the formulation proposed by Gent and McWilliams, 1990), and exchange energy via up- or down-gradient eddy momentum fluxes (traditionally parameterized via eddy viscosities). We propose a new parameterization that combines existing formulations of eddy fluxes in an energetically consistent way, and that can be applied at both “non-eddying” and “eddy permitting”’ resolutions. The parameterization has been implemented in GFDL’s Modular Ocean Model (MOM6) and performs well over a range of resolutions, seamlessly connecting the traditional “non-eddying” and “eddy permitting” regimes. The results also point towards limitations in our theoretical understanding of eddy energetics that need to be addressed in order to further improve the formulation of eddy parameterizations, highlighting in particular the need to better understand the routes to dissipation of mesoscale eddy energy.