Near-inertial dissipation due to stratified flow over abyssal topography

This is a Preprint and has not been peer reviewed. This is version 1 of this Preprint.

Downloads

Download Preprint

Authors

Varvara E Zemskova , Nicolas Grisouard 

Abstract

Linear theory for steady stratified flow over topography sets the range for topographic wavenumbers over which freely propagating internal waves are generated, and the radiation and breaking of these waves contribute to energy dissipation away from the ocean bottom. However, previous numerical work demonstrated that dissipation rates can be enhanced by flow over large scale topographies with wavenumbers outside of the lee wave radiative range.
We conduct idealized 3D numerical simulations of steady stratified flow over 1D topography in a rotating domain and quantify vertical distribution of kinetic energy dissipation. We vary two parameters: the first determines whether the topographic obstacle is within the lee wave radiative range and the second, proportional to the topographic height, measures the degree of flow non-linearity. For a certain combination of topographic width and height, the flow develops periodicity in wave breaking and kinetic energy dissipation; in these simulations, kinetic energy dissipation rates are also enhanced in the interior of the domain. In the radiative regime the inertial motions arise due to resonant wave-wave interactions. In the small wavenumber non-radiative regime, instabilities downstream of the obstacle can facilitate the generation and propagation of non-linearly forced inertial motions, especially as topographic height increase. In our simulations, dissipation rates for tall and wide non-radiative topography are comparable to those of radiative topography, even away from the bottom, which is relevant to the ocean where the topographic spectrum is such that wider abyssal hills also tend to be taller.

DOI

https://doi.org/10.31223/X58319

Subjects

Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Keywords

internal waves, stratified flow, bottom topography, topography-driven flow, energy dissipation, abyssal topography, rotating stratified flow, numerical simulations

Dates

Published: 2021-01-12 15:51

License

CC BY Attribution 4.0 International

Additional Metadata

Data Availability (Reason not available):
All Nek5000 code necessary to run the simulations presented in this paper and all Python code for used for post-processing at https://github.com/bzemskova/bottom_topography_flow

Add a Comment

You must log in to post a comment.


Comments

There are no comments or no comments have been made public for this article.