Near-Inertial Wave Transmission to Ocean Interior in Realistic Global Ocean Simulations

Near-inertial waves (NIWs) play a crucial role in transmitting wind energy from the ocean surface into the interior, thereby providing a major energy source for ocean mixing. The NIW energy transmission is significantly modulated by background mesoscale vorticity. It is not yet clear how the mesoscale vorticity affects the downward energy transmission on a global scale.

Hence, we study the generation, propagation and dissipation of wind generated NIWs using global 1/25° Hybrid Coordinate Ocean Model (HYCOM) simulations with and without realistic tidal forcing. The model has 41 layers with uniform vertical coordinates in the mixed layer and isopycnal coordinates in the ocean interior. The model is forced by 1/3hr wind from the NAVGEM atmospheric model. We analyze one month of model data for May-June 2019. We compute the near-inertial wave energetics, such as the wind input, flux divergence and dissipation for the undecomposed 3D fields. Moreover, we also project the 3D HYCOM fields on vertical normal modes to compute similar energy terms per mode. We find that the global wind energy input to near-inertial motions is about 0.25 TW for the 30-day period and is consistent with previous studies. The NIW energy transmission is estimated from the vertical energy flux at different depths. We find that regions with high mesoscale energy have enhanced near-inertial wind energy input and NIW transmission to the interior.