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Is the Cromwell current driven by equatorial Rossby waves?

Published online by Cambridge University Press:  28 March 2006

Walter Munk  and
Dennis Moore
Walter Munk
Affiliation:
Departments of Meteorology and Geology and Geophysics, Massachusetts Institute of Technology
On sabbatical leave from the Institute of Geophysics and Planetary Physics, University of California, San Diego, La Jolla, California.
Dennis Moore
Affiliation:
Division of Engineering and Applied Physics, Harvard University
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Abstract

A second-order theory for equatorial, baroclinic Rossby waves in a bounded ocean yields, among other components, terms of zero frequency. We inquire whether the associated rectified flow (or ‘streaming’, or ‘mass transport’) can be related to the submerged equatorial jet observed by Cromwell, Knauss and others. For quite reasonable models of baroclinic Rossby waves, the resultant streaming can be sharply concentrated at the equator, and varies in depth as N(z), thus giving maximum flow at the thermocline (where the Väisälä frequency N(z) is largest). In this way the rectification hypothesis might account for the observed submerged equatorial steering of the Cromwell current. The observed direction of streaming calls for a predominance of equatorially symmetric Rossby waves. The observed magnitude implies that the r.m.s. fluctuations be of the same order as the mean current; that is to say, we have applied weakinteraction theory to a strong-interaction problem. There are other difficulties.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 33 , Issue 2 , 12 August 1968 , pp. 241 - 259
Copyright
© 1968 Cambridge University Press

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