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The propagation and decay of a coastal vortex on a shelf

Published online by Cambridge University Press:  29 September 2021

Matthew N. Crowe*
Affiliation:
Department of Mathematics, University College London, London WC1E 6BT, UK
Edward R. Johnson
Affiliation:
Department of Mathematics, University College London, London WC1E 6BT, UK
*
Email address for correspondence: m.crowe@ucl.ac.uk

Abstract

A coastal eddy is modelled as a barotropic vortex propagating along a coastal shelf. If the vortex speed matches the phase speed of any coastal trapped shelf wave modes, a shelf wave wake is generated leading to a flux of energy from the vortex into the wave field. Using a simple shelf geometry, we determine analytic expressions for the wave wake and the leading-order flux of wave energy. By considering the balance of energy between the vortex and wave field, this energy flux is then used to make analytic predictions for the evolution of the vortex speed and radius under the assumption that the vortex structure remains self-similar. These predictions are examined in the asymptotic limit of small rotation rate and shelf slope and tested against numerical simulations. If the vortex speed does not match the phase speed of any shelf wave, steady vortex solutions are expected to exist. We present a numerical approach for finding these nonlinear solutions and examine the parameter dependence of their structure.

Type
JFM Papers
Copyright
© The Author(s), 2021. Published by Cambridge University Press

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References

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