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Instability of wind-forced inertial oscillations

Published online by Cambridge University Press:  26 April 2006

A. M. Treguier
Affiliation:
Laboratoire de Physique des Océans, IFREMER, Centre de Brest, BP70, 29280 Piouzané, France
P. Klein
Affiliation:
Laboratoire de Physique des Océans, IFREMER, Centre de Brest, BP70, 29280 Piouzané, France

Abstract

An instability mechanism that can amplify wind-forced inertial oscillations in the upper ocean is investigated. This forced instability happens because of the phase relationship between the mixed-layer depth and the surface current. It allows the inertial oscillations propagating against the wind to extract energy from it and amplify. The key ingredients for the instability to work are (a) a non-zero mean wind stress, (b) a spatial variability of the oscillations in the direction of the wind stress. The amplification is demonstrated using a simple shallow-water model in a few situations: the dispersion of a localized disturbance with steady and time-varying wind forcing, generation of inertial waves at a coast, and spatial variability induced by mesoscale eddies. Estimates of the growth rate are provided for both dissipative and non-dissipative cases.

Type
Research Article
Copyright
© 1994 Cambridge University Press

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