Re-Energizing Ocean Mesoscale Eddies: Assessing Backscatter Parameterizations for Global Ocean Models

Course resolution ocean models (e.g., at ~1 degree) are unable resolve mesoscale eddies over most of the ocean. To compensate for this limitation, an isopycnal height diffusion is used to mimic the restratifying effects of the unresolved eddies. However, at eddy-permitting resolutions (e.g., ~1/4 degree), isopycnal height diffusion strongly damps baroclinic eddies, reducing the effective resolution of the model. To address the challenge of parametrizing eddies in eddy-permitting models, a variety of `backscatter schemes’ have been devised. These schemes reintroduce excessively dissipated kinetic energy back into the resolved ocean circulation. However, determining the optimal use of these backscatter schemes in global ocean models remains an open question. Proposed solutions range from the simultaneous application of both isopycnal height diffusion and backscatter at the same locations to disregarding isopycnal height diffusion and exclusively relying on backscatter. Here, we investigate these different strategies with the objective of identifying the optimal eddy parameterization to enhance the accuracy of the ocean component of CESM3 at an eddy-permitting resolution. By addressing the challenge of representing mesoscale eddies in climate models, this research contributes to a more accurate understanding of Earth's climate system.