Coronavirus Information for the UC San Diego Community

Our leaders are working closely with federal and state officials to ensure your ongoing safety at the university. Stay up to date with the latest developments. Learn more.

A three-component model for the coupled evolution of near-inertial waves, quasi-geostrophic flow and the near-inertial second harmonic

TitleA three-component model for the coupled evolution of near-inertial waves, quasi-geostrophic flow and the near-inertial second harmonic
Publication TypeJournal Article
Year of Publication2016
AuthorsWagner G.L, Young W.R
JournalJournal of Fluid Mechanics
Volume802
Pagination806-837
Date Published2016/09
Type of ArticleArticle
ISBN Number0022-1120
Accession NumberWOS:000390097200006
Keywordsdeep-ocean; dispersion; energy; internal waves; layer; mesoscale eddy field; ocean processes; oscillations; propagation; quasi-geostrophic flows
Abstract

We derive an asymptotic model that describes the nonlinear coupled evolution of (i) near-inertial waves (NIWs), (ii) balanced quasi-geostrophic flow and (iii) near-inertial second harmonic waves with frequency near 2f(0), where f(0) is the local inertial frequency. This 'three-component' model extends the two-component model derived by Xie & Vanneste (J. Fluid Mech., vol 774, 2015, pp. 143-169) to include interactions between near-inertial and waves. Both models possess two conservation laws which together imply that oceanic NIWs forced by winds, tides or flow over bathymetry can extract energy from quasi-geostrophic flows. A second and separate implication of the three-component model is that quasi-geostrophic flow catalyses a loss of NIW energy to freely propagating waves with near-2f(0) frequency that propagate rapidly to depth and transfer energy back to the NIW field at very small vertical scales. The upshot of near-2f(0) generation is a two-step mechanism whereby quasi-geostrophic flow catalyses a nonlinear transfer of near-inertial energy to the small scales of wave breaking and diapycnal mixing. A comparison of numerical solutions with both Boussinesq and three-component models for a two-dimensional initial value problem reveals strengths and weaknesses of the model while demonstrating the extraction of quasi-geostrophic energy and production of small vertical scales.

DOI10.1017/jfm.2016.487
Short TitleJ. Fluid Mech.
Student Publication: 
No
Research Topics: 
sharknado