Internal Tide Generation in the Deep Ocean

TLDR

Internal tides are gravity waves generated when barotropic tidal currents interact with variable bottom topography, dissipating tidal energy and driving deep‑ocean mixing, with key parameters being the ratio of tidal excursion to topographic scale, bottom slope relative to internal‑wave ray angle, and topographic height to ocean depth. Theoretical work indicates that in the deep ocean most internal‑tide energy flux is carried by low‑mode waves that propagate away from the generation site, is largely insensitive to bottom slope for isolated features, and that intense energy beams form near critical slopes, enhancing local mixing.

Abstract

Internal tides are internal gravity waves generated in stratified waters by the interaction of barotropic tidal currents with variable bottom topography. They play a role in dissipating tidal energy and lead to mixing in the deep ocean. Key dimensionless parameters governing their generation include the tidal excursion compared with the scale of the topography, the bottom slope compared with the angle at which rays of internal waves of tidal frequency propagate, and the height of the topography compared with the depth of the ocean. Recent theoretical developments for parts of this parameter space particularly relevant to the deep ocean show that most of the energy flux is associated with low modes that propagate away from the generation region. For isolated features this energy flux is not strongly dependent on the bottom slope. Intense beams of internal tidal energy are expected near “critical slopes," bottom slopes equal to the ray slope, and lead to local mixing.