Numerical study of the bottom-intensified tidal mixing using an "eikonal approach"

Abstract

Locally enhanced turbulent mixing above abyssal rough bottom bathymetry is one of the candidates that might make up for the lack of diapycnal diffusivity in maintaining the global overturning circulation. In the present study, we carry out a series of numerical experiments using an eikonal approach to examine the vertical distribution of energy dissipation rates caused by breaking of the semidiurnal internal tide. Special attention is directed to the physical parameters that control the magnitude and vertical decay scale of the bottom-intensified mixing. It is shown that breaking of internal tides with horizontal scales much less than 1 km is responsible for bottom-intensified mixing. There is an inevitable trade-off between the magnitude and the vertical decay scale of bottom-intensified mixing so that tidal interactions with abyssal rough bottom bathymetry are unlikely to create mixing hot spots intensive enough to affect the global overturning circulation. Copyright 2009 by the American Geophysical Union.