Internal Swell Generation: The Spatial Distribution of Energy Flux from the Wind to Mixed Layer Near-Inertial Motions

Abstract

The energy flux from the wind to inertial mixed layer motions is computed for all oceans from 50 8 St o 508N for the years 1996‐99. The wind stress, t, is computed from 6-h, 2.58-resolution NCEP‐NCAR global reanalysis surface winds. The inertial mixed layer response, uI, and the energy flux, P5 t · uI, are computed using a slab model. The validity of the reanalysis winds and the slab model is demonstrated by direct comparison with wind and ADCP velocity records from NDBC buoys. (At latitudes . 508, the inertial response is too fast to be resolved by the reanalysis wind 6-h output interval.) Midlatitude storms produce the greatest fluxes, resulting in broad maxima near 40 8 latitude during each hemisphere’s winter, concentrated in the western portion of each basin. Northern Hemisphere fluxes exceed those in the Southern Hemisphere by about 50%. The global mean energy flux from 1996 to 1999 and 508 St o 508N is (0.98 6 0.08) 3 1023 Wm 22, for a total power of 0.29 TW (1 TW 5 1012 W). This total is the same order of magnitude as recent estimates of the global power input to baroclinic M2 tidal motions, suggesting that windgenerated near-inertial waves may play an important role in the global energy balance.