Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude

Richet O, Chomaz J-M, MULLER CJ. 2018. Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude. Journal of Geophysical Research: Oceans. 123(9), 6136–6155.


Journal Article | Published | English
Author
Richet, O.; Chomaz, J.-M.; MULLER, Caroline JIST Austria
Abstract
Several studies have shown the existence of a critical latitude where the dissipation of internal tides is strongly enhanced. Internal tides are internal waves generated by barotropic tidal currents impinging rough topography at the seafloor. Their dissipation and concomitant diapycnal mixing are believed to be important for water masses and the large‐scale ocean circulation. The purpose of this study is to clarify the physical processes at the origin of this strong latitudinal dependence of tidal energy dissipation. We find that different mechanisms are involved equatorward and poleward of the critical latitude. Triadic resonant instabilities are responsible for the dissipation of internal tides equatorward of the critical latitude. In particular, a dominant triad involving the primary internal tide and near‐inertial waves is key. At the critical latitude, the peak of energy dissipation is explained by both increased instability growth rates, and smaller scales of secondary waves thus more prone to break and dissipate their energy. Surprisingly, poleward of the critical latitude, the generation of evanescent waves appears to be crucial. Triadic instabilities have been widely studied, but the transfer of energy to evanescent waves has received comparatively little attention. Our work suggests that the nonlinear transfer of energy from the internal tide to evanescent waves (corresponding to the 2f‐pump mechanism described by Young et al., 2008, https://doi.org/10.1017/S0022112008001742) is an efficient mechanism to dissipate internal tide energy near and poleward of the critical latitude. The theoretical results are confirmed in idealized high‐resolution numerical simulations of a barotropic M2 tide impinging sinusoidal topography in a linearly stratified fluid.
Publishing Year
Date Published
2018-09-01
Journal Title
Journal of Geophysical Research: Oceans
Volume
123
Issue
9
Page
6136-6155
ISSN
IST-REx-ID

Cite this

Richet O, Chomaz J-M, MULLER CJ. Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude. Journal of Geophysical Research: Oceans. 2018;123(9):6136-6155. doi:10.1029/2017jc013591
Richet, O., Chomaz, J.-M., & MULLER, C. J. (2018). Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude. Journal of Geophysical Research: Oceans. American Geophysical Union. https://doi.org/10.1029/2017jc013591
Richet, O., J.-M. Chomaz, and Caroline J MULLER. “Internal Tide Dissipation at Topography: Triadic Resonant Instability Equatorward and Evanescent Waves Poleward of the Critical Latitude.” Journal of Geophysical Research: Oceans. American Geophysical Union, 2018. https://doi.org/10.1029/2017jc013591.
O. Richet, J.-M. Chomaz, and C. J. MULLER, “Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude,” Journal of Geophysical Research: Oceans, vol. 123, no. 9. American Geophysical Union, pp. 6136–6155, 2018.
Richet O, Chomaz J-M, MULLER CJ. 2018. Internal tide dissipation at topography: Triadic resonant instability equatorward and evanescent waves poleward of the critical latitude. Journal of Geophysical Research: Oceans. 123(9), 6136–6155.
Richet, O., et al. “Internal Tide Dissipation at Topography: Triadic Resonant Instability Equatorward and Evanescent Waves Poleward of the Critical Latitude.” Journal of Geophysical Research: Oceans, vol. 123, no. 9, American Geophysical Union, 2018, pp. 6136–55, doi:10.1029/2017jc013591.
All files available under the following license(s):
Copyright Statement:
This Item is protected by copyright and/or related rights. [...]

Link(s) to Main File(s)
Access Level
OA Open Access

Export

Marked Publications

Open Data IST Research Explorer

Search this title in

Google Scholar