Energy Cascade and Dynamics of Internal Waves on a Subtropical Continental Shelf: Part 1 - Internal Tides

During the summer of 2002 (a typical summer stratification scenario), internal waves were observed on the South Brazil Bight (SBB), concomitant to Atlantic Central Water uplifting and internal tidal dynamics, with the M2 frequency contributing nearly 10 %  of the energy spectrum. Using 1 km horizontal resolution Regional Ocean Modeling System (ROMS) simulations, we examine internal tide generation and interaction within the SBB, identifying significant spatial variability, with offshore energy hotspots influenced by the supercritical topography, topographic features, and the Brazil Current, culminating in 8.70 % of all converted energy generated 5.204 GW in the slope at only 1.64  % of the area. These features extend the residence time of Mode 1 M2 internal tide 5 days longer than the theory predicts, enhancing nonlinear interactions to the level where the wave-wave interactions matter equally as the wave-mean flow interactions, transferring energy to higher frequencies and sustaining baroclinic energy in shallower waters, where stratification breaks down rapidly. Approximately 16.18 %  of barotropic-to-baroclinic M2 energy cascades to higher harmonics, while 63.73 %  is reflected. Scattered energy supports weakly incoherent internal waves at depths shallower than 200 m, driving a nearly closed energy budget in the model. The Internal Tide enhances up to 21 %  of the vertical mixing diffusivity mostly at the bottom and enhances lower temperature advection and the thermal diffusivity coefficient while reducing the vertical potential temperature gradient mostly at the surface and subsurface. Future work will explore the role of wind-driven internal waves and their interactions with the Brazil Current in enhancing mixing, with a focus on topographic conversion hotspots and remote internal wave reflections.