Poleward coastal jets induced by westerlies in the Bay of Biscay

Type Publication
Date 2012-03
Language English
Copyright 2012 AGU
Author(s) Batifoulier Francois1, 2, Lazure Pascal1, Bonneton Philippe2
Affiliation(s) 1 : IFREMER, Ctr Brest, F-29280 Plouzane, France.
2 : Univ Bordeaux 1, UMR CNRS EPOC 5805, F-33405 Talence, France.
Source Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2012-03 , Vol. 117 , N. C03023 , P. 19 pp.
DOI 10.1029/2011JC007658
WOS© Times Cited 11
Abstract Two hydrodynamic surveys based on acoustic Doppler current profiler (ADCP) and drift buoys measurements taken in summer 2008 and 2009 revealed poleward coastal jets of up to 32 cm s(-1) that lasted up to 22 d along the Aquitaine shelf in the southeastern area of the Bay of Biscay. A strong increase in bottom temperature was associated with these currents, up to 4 degrees C in 5 d at 54 m depth. These observations occurred after a few days of westerlies, cross-shore winds which were thought to have only a limited impact on longshore circulation. Here, the MARS3D hydrodynamic model was used with a schematic bathymetry of the southeastern area of the Bay of Biscay to reproduce and analyze these coastal jets. Simulations revealed that the triggering mechanism of the poleward currents is unequivocally due to downwelling circulation induced along the Spanish coast. This downwelling induces an external longshore pressure gradient which generates a high-speed coastal-trapped wave that propagates along the French coast with a phase velocity of about 3 to 4 m s(-1) and an internal baroclinic Kelvin wave with a phase velocity of about 1 m s(-1). A sensitivity study of the role of stratification conditions, wind strength and duration was then carried out to determine the periods that are the most sensitive to this wind-induced circulation.
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