Open AccessPoleward coastal jets induced by westerlies in the Bay of Biscay
Author(s) -
Batifoulier Francois,
Lazure Pascal,
Bonneton Philippe
Publication year - 2012
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2011jc007658
Subject(s) - downwelling , bay , westerlies , geology , oceanography , stratification (seeds) , longshore drift , acoustic doppler current profiler , kelvin wave , bathymetry , baroclinity , circulation (fluid dynamics) , climatology , atmospheric sciences , current (fluid) , upwelling , geomorphology , sediment transport , sediment , physics , botany , germination , dormancy , biology , thermodynamics , seed dormancy
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°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.