On the Generation of Bottom-Trapped Internal Tides

Abstract

AbstractThe interaction of the barotropic tide with bottom topography when the tidal frequency ω is smaller than the Coriolis frequency f is examined. The resulting waves are called bottom-trapped internal tides. The energy density associated with these waves is computed using linear wave theory and vertical normal-mode decomposition in an ocean of finite depth. The global calculation of the modal energy density is performed for the semidiurnal M2 tidal constituent and the two major diurnal tidal constituents K1 and O1. An observationally based decay time scale of 3 days is then used to transform the energy density to energy flux in units of watts per square meter. The globally integrated energy fluxes are found to be 1.99 and 1.43 GW for the K1 and O1 tidal constituents, respectively. For the M2 tidal constituent, it is found to be 1.15 GW. The Pacific Ocean is found to be the most energetic basin for the bottom-trapped diurnal tides. Two regional estimates of the bottom-trapped energy flux are given for the Kuril Islands and the Arctic Ocean, in which the bottom-trapped waves play a role for the tidally induced vertical mixing. The results of this study can be incorporated into ocean general circulation models and coupled climate models to improve the parameterization of the vertical mixing induced by breaking of the internal tides.