Shortwave Instabilities of Coastal Currents

Nathan Paldor, Michael Ghil

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The finite-wavelength instability of a two-layer, inviscid coastal current is investigated numerically over a wide range of parameters, and verified analytically in a simple limiting case. We show that the instability exponents increase linearly with wavenumber and that they increase with the upper layer's mean speed. A comparison with Kelvin-Helmholtz instabilities shows both similarities and differences. For large total ocean depth, our theory predicts the existence of very vigorous instabilities whenever the slanting interface between layers extends close to the bottom on the ocean. The energy source of these instabilities is mixed barotropic-baroclinic. The theory presented here ceases to be valid at large wavenumbers, where viscous effects have to be included in the governing equations. An ad hoc extension of the inviscid theory agrees with the spatial and temporal scales of observed, finite-amplitude features in the Algerian Current, for a reasonable value of the eddy-viscosity coefficient.

Original languageEnglish
Pages (from-to)225-241
Number of pages17
JournalGeophysical and Astrophysical Fluid Dynamics
Volume58
Issue number1-4
DOIs
StatePublished - Jul 1991
Externally publishedYes

Keywords

  • coastal currents
  • frontal instabilities
  • Kelvin-Helmholtz instability
  • ocean

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