Global estimates of wind energy input to subinertial motions in the Ekman-Stokes layer

By incorporating the wave-induced Coriolis-Stokes forcing into the classical Ekman model, the wind energy input to the Ekman-Stokes layer is investigated, with an emphasis on the surface wave effects when the direction of Stokes drift deviates from that of wind stress. Theoretical analysis of the kinetic energy balance of the Ekman-Stokes layer shows that the total wind energy input consists of the direct wind energy input and the wave-induced energy input. Details of the direct wind and wave-induced energy input are discussed. Based on the ECMWF ERA-40 Re-Analysis wind stress and surface wave data, the global total wind energy input to subinertial motions in the Ekman-Stokes layer is estimated at 2.19 TW, including 0.26 TW (12%) wave-induced energy input and 1.93 TW (88%) direct wind energy input. The effect of sea-ice coverage on the energy input to the Ekman-Stokes layer is also considered. It is shown that the global total energy input could be overestimated by 0.08 TW (about 4%) without taking the sea-ice coverage into account.