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Dynamics of internal waves induced by stratified flow over abyssal topography

Ocean observations and numerical simulations have shown that energy dissipation rate can be enhanced in the ocean through internal waves breaking over topographical features. As these waves travel over long distances and the energy dissipation effects can persists over 20-30 km away from an abyssal hill, they have a substantial impact on the global ocean circulation, density structure, and mixing. Energy generation and dissipation via internal waves is of particular interest in the Southern Ocean and over oceanic ridges, which are climatologically sensitive regions in that they play important roles in meridional transport, oxygenation of deep waters, and carbon sequestration.

Direct measurements of energy dissipation and mixing are extremely difficult to obtain, and thus are globally sparse. Because of the spatial resolution constraints, in global models, energy radiation and dissipation rates from flows over small-scale rough topography are parametrized using linear lee wave theory. However, recent observational and numerical studies presented discrepancies with the linear theory. In this study, I use an idealized numerical model to explore how the height and the width of a topographic feature affect flow dynamics, internal wave radiation, and dissipation rates. Interestingly, in the simulations with certain height/width combinations, dissipation rates exhibit temporal periodicity due to the interactions between lee and inertial waves. Furthermore, contrary to the linear theory, I find that wide abyssal hills could have significant contribution to dissipation near the topography and in the ocean interior.

Event series  Brewer-Wilson Seminar Series