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

Using 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. Plain Language Summary For maintaining the oceanic overturning circulation, energy is needed to mix the dense water up and light water down. The main energy source for mixing arises from breaking of internal waves. A considerable portion of this source comes from waves excited by winds at the sea surface. This paper quantifies this wave energy source based on a frontier simulation of a coupled atmosphere‐ocean general circulation model at a horizontal resolution of 5 km. This model is capable to simulate tropical cyclones (hurricanes and typhoons) and less‐extreme small‐scale and short‐living weather disturbances and oceanic mesoscale eddies, which were not represented by the models used in most of the previous studies. Taking these new features into account, we find that the wind‐induced wave energy source is less than 0.1 TW. Key Points Relatively low wind power input to near‐inertial motions in a 5 km global coupled simulation Energy flux radiating from the mixed layer bottom as interior