Focusing and vertical mode scattering of the first mode internal tide by mesoscale eddy interaction

Abstract

Numerical experiments are performed using the MITgcm to investigate the interaction of a mode-one internal tide with barotropic and baroclinic mode-one mesoscale eddies. Results show that after a mode-one internal tide passes through a barotropic eddy, spatial hot and cold spots of energy flux are produced in beam-like patterns. The magnitude of the energy flux in the hot spots can exceed twice the incident flux while in the cold spots can reach nearly zero. Passing a mode-one internal tide through a mode-one baroclinic eddy results in the scattering of energy from the incident mode-one to modes two and higher. The higher mode waves are produced in beam-like patterns. For the parameter regime explored here, we find conversion efficiencies that reach 13% for eddies of diameter 120 km. The Rossby numbers for our experiments are order one, corresponding to energetic mesoscale eddies that are typically found in western boundary current extensions and in the southern ocean. These eddies have length scales comparable to those of low-mode internal tides, and we expect that interaction between the two will be easily formed in locations where these phenomena coexist. ©2013. American Geophysical Union. All Rights Reserved.