Oceanic Mesoscale Eddy Depletion Catalyzed by Internal Waves

The processes leading to the depletion of oceanic mesoscale kinetic energy (KE) and the energization of near-inertial internal waves are investigated using a suite of realistically forced regional ocean simulations. By carefully modifying the forcing fields we show that solutions where internal waves are forced have similar to 25% less mesoscale KE compared with solutions where they are not. We apply a coarse-graining method to quantify the KE fluxes across time scales and demonstrate that the decrease in mesoscale KE is associated with an internal wave-induced reduction of the inverse energy cascade and an enhancement of the forward energy cascade from sub-to super-inertial frequencies. The integrated KE forward transfer rate in the upper ocean is equivalent to half and a quarter of the regionally averaged near-inertial wind work in winter and summer, respectively, with the strongest fluxes localized at surface submesoscale fronts and filaments.

Automated summary

By modifying the forcing fields and using a coarse-graining method, it is found that the presence of internal waves leads to a reduction of approximately 25% in oceanic mesoscale kinetic energy. The internal waves induce a decrease in the inverse energy cascade and an enhancement in the forward energy cascade, affecting the transfer rate of mesoscale KE in the ocean.