Wind Power Input to Ocean Near‐Inertial Waves Diagnosed From a 5‐km Global Coupled Atmosphere‐Ocean General Circulation Model

Abstract

AbstractUsing the 5 km coupled general circulation model ICON, the surface internal wave energy source, crucial for the oceanic circulation, is quantified as the wind‐induced wave energy flux that radiates from the mixed layer bottom (MLB) into the ocean interior. Our result lowers the previous estimates of the wind power input to surface near‐inertial motions from up to more than 1 TW down to about 0.23–0.27 TW, depending on season. We point out that the estimate of the wind input to ocean depends not only on the wind stress used—as suggested by previous studies—but also on the ocean model used. While the surface currents in a slab ocean model or a non‐eddying ocean circulation model are strongly determined by the wind forcing, the surface currents in the 5 km ICON model can be more strongly determined by internal instability process (eddy) than by wind stress forcing from less‐extreme weather disturbances. The resulting more or less random alignment of surface current and wind stress can presumably lead to a lower wind input to surface near‐inertial motions. Of the surface wave energy source, about 30% is fluxed down into the interior ocean. This percentage roughly doubles those from previous studies, due to the stronger wave energy flux related to stronger inertial waves generated by the tropical cyclones simulated by the 5 km ICON model. Overall, the low wind input at near‐inertial frequencies produces a wind‐induced wave energy source at the MLB that is well below 0.1 TW.