767 / 2024-09-19 11:53:54

Response of ocean circulations to the vertical structure of eddy momentum parameterization

Mesoscale eddies, ocean circulations, parameterization

Ocean mesoscale eddies play a pivotal role in the transport of momentum, heat, carbon, and other properties in the ocean, significantly impacting climate dynamics. State-of-the-art ocean climate models, which partially resolve mesoscale eddies (i.e., eddy-permitting), requires parameterizations to account for the missing energy cascade to the resolved flow. The kinetic energy backscatter parameterization has been employed to represent the impact of subgrid eddy momentum flux in eddy-permitting simulations. However, the vertical structure of the backscatter remains unconstrained, limiting the evaluation of its impact on large-scale circulations. This study implements a novel parameterization for the vertical structure of the backscatter and evaluates its impact on large-scale circulations in both idealized and realistic eddy-permitting simulations of Modular Ocean Model (MOM6). The backscatter parameterization enhances the global kinetic energy and the transport of gyre circulations by energizing mesoscale eddies and their interactions with the mean flow. The vertical structure of backscatter shapes the vertical profile of mesoscale eddies, which further modulate the large-scale circulation through eddy momentum flux and inverse energy cascade. A vertical structure described by the surface quasigeostrophic dynamics improves the large-scale isopycnal structure by reasonably representing the momentum flux of surface-intensified eddies. These results indicate a crucial role of the vertical structure of eddies in the mesoscale parameterization and eddy-mean flow interactions.