Remotely forced biweekly deep oscillations on the continental slope of the Gulf of Guinea

Type Article
Date 2008-06
Language English
Author(s) Guiavarc'h Catherine1, 3, Treguier Anne-Marie1, 3, Vangriesheim Annick2
Affiliation(s) 1 : IFREMER, Lab Phys Oceans, Plouzane, France.
2 : IFREMER, Lab Environm Profond, Plouzane, France.
Source Journal of Geophysical Research ( JGR ) - Oceans (0148-0227) (American Geophysical Union), 2008-06 , Vol. 113 , N. C06002 , P. NIL_1-NIL_14
DOI 10.1029/2007JC004471
WOS© Times Cited 11
Keyword(s) Gulf of Guinea, numerical modeling, Coastal trapped waves
Abstract Current meter measurements on the continental slope of the Gulf of Guinea (at 7 degrees 20'S and 1300 m depth) have revealed biweekly oscillations of the currents, bottom intensified and oriented along the bathymetry. We develop a three-dimensional primitive equation model of the Gulf of Guinea to study the oscillations and their forcing mechanism. The high resolution (1/12 degrees) regional model reproduces remarkably well the main characteristics of the deep currents on the continental slope. Experiments with different forcings demonstrate that the biweekly variability at 1300 m depth is remotely forced by equatorial winds. Deep Yanai waves generated by the wind propagate eastward along the equator. Upon reaching the African coast, the energy propagates poleward in both directions as coastal trapped waves. The selection of the dominant biweekly period is explained by the absence of equatorial waves with westward group velocities in that frequency band. Contrary to a previous hypothesis involving tidal forcing, our interpretation is coherent with the significant interannual variability of the biweekly energy.
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