Eddy-internal waves interactions and their contribution to cross-scale energy transfers in the ocean

The ocean is forced at large scales by fluxes of momentum and buoyancy. Yet, climate equilibrium can only be reached through the dissipation of these energy sources, which occur at much smaller scales. Understanding how energy is transferred across this wide range of scales and the routes to dissipation are therefore key to understand the ocean response to future climate scenarios and remains a central challenge in physical oceanography. While the inverse kinetic energy cascade associated with geostrophic turbulence has been extensively studied, the direct cascade of kinetic energy and the processes that enable energy transfer towards dissipative scales remain incompletely understood and poorly constrained in global ocean models.
In this talk, we review some of the recent work achieved in identifying and quantifying the processes leading to cross-scale energy fluxes using flow decomposition methods and spectral fluxes analyses, applied to realistic high-resolution simulations forced with eddies and internal waves. We show how the interaction between eddies and internal waves are central in enhancing the direct energy cascade –as opposed to the common paradigm relying on interactions among internal waves–, and in reducing the inverse energy cascade. We describe as well the physical processes underlying these interactions.
These studies establish eddy–internal wave interactions as a fundamental component of the ocean energy budget, with implications for mixing, dissipation, and the parameterization of sub grid scale processes in ocean models.