Internal Tide Interactions with Submesoscale and Mesoscale Eddies in the Tropical Western Atlantic

The cross-scale energy exchange between wave and nonwave motions is crucial in determining the ocean energy redistribution. The interaction of mesoscale and submesoscale eddies with internal tides is a key driver of this cross-scale energy exchange but remains poorly understood. In this study, we characterize this process by analyzing high-resolution simulations using a regional model of the tropical western Atlantic. A Lagrangian filter is implemented to separate the dynamical fields into wave and nonwave motions and account for Doppler shifts. An Eulerian filter is then applied to extract the internal tide from the wave motion. The nonwave component is further separated into mesoscale and submesoscale motions. The interactions between the internal tides and the submesoscale are distinct from the interactions with the mesoscale. Horizontally, energy transfer predominantly occurs at regions of intense strain where eddies intersect. The interaction between the mesoscale and internal tides can vary in the direction of energy transfer in different regions, while the submesoscale and internal tide interactions tend to facilitate a forward energy transfer to the internal tides. Vertically, both the vertical wave stress term and the potential energy conversion term are significant and are primarily controlled by the vertical shear of the nonwave components. Internal tide interactions with the mixed layer–instability-dominated submesoscales exhibit significant seasonal dependence, whereas those with frontogenesis-dominated submesoscales do not. The depth-averaged energy exchange is on the same order as the observed dissipation rate of internal tides, indicating this interaction can act as a significant source or sink of internal tide energy.