Global Estimates of Near-Inertial Internal Wave Generation

Samuel Maurice Kelly, University of Minnesota Duluth, Duluth, MN, United States, Maarten C Buijsman, University of Southern Mississippi, Stennis Space Center, MS, United States, Keshav Raja, Universiy of Southern Mississippi, School of Ocean Science and Engineering, John C. Stennis Space Center, MS, United States and Harper L Simmons, University of Alaska Fairbanks, Fairbanks, AK, United States
Abstract:
Wind work supplies 0.3-1.5 TW to near-inertial motions in the surface boundary layer. Converging and diverging mixed-layer currents generate near-inertial internal waves (NIWs) that radiate downward, supplying mechanical energy that mixes the stratified interior. Spatiotemporal wind variability, meanflow interactions with inertial oscillations, and latitudinal variation in the inertial frequency generate NIWs, however, the global contribution of each source is unknown. Here, we use a linear Coupled-mode Shallow Water model (CSW) to quantify the contribution of each source of NIWs in global simulations with observed winds, mixed-layer currents, and topography. These simulations are then compared with a semi-analytical model of NIW generation by a vibrating membrane that represents the base of the mixed layer. Finally, wind work and NIW generation in the linearized model are compared with those produced in fully-nonlinear global HYCOM simulations and regional North Atlantic ROMS simulations. The collective results emphasize that meanflow interactions with mixed-layer inertial oscillations enhance NIW generation, particularly at high wavenumbers, consistent with previous investigations.