Parameterizing tidal dissipation over rough topography

TLDR

Traditional tidal dissipation models rely on bottom boundary layer drag, which is weak in the deep ocean, whereas internal waves generated over rough topography dominate energy transfer there. The authors incorporate a parameterization of internal‑wave drag over rough topography into a barotropic tide model. Adding this mechanism improves ocean tide models, substantially raising deep‑ocean dissipation to match TOPEX/Poseidon altimetry estimates.

Abstract

The traditional model of tidal dissipation is based on a frictional bottom boundary layer, in which the work done by bottom drag is proportional to a drag coefficient and the velocity cubed. However, away from shallow, coastal regions the tidal velocities are small, and the work done by the bottom boundary layer can account for only weak levels of dissipation. In the deep ocean, the energy flux carried by internal waves generated over rough topography dominates the energy transfer away from barotropic flow. A parameterization for the internal wave drag over rough topography is included as a dissipative mechanism in a model for the barotropic tides. Model results suggest that the inclusion of this dissipation mechanism improves hydro‐dynamical models of the ocean tide. It also substantially increases the amount of modeled tidal dissipation in the deep ocean, bringing dissipation levels there into agreement with recent estimates from TOPEX/Poseidon altimetry data.