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Echanges côtes-large et propriétés biogéochimiques dans les régions d'upwelling de bord Est

Abstract : This thesis aims to advance in understanding the variability of the biogeochemical properties in eastern boundary upwelling systems. Surface chlorophyll concentration estimated from space is analyzed over the region along the northwest African coast. Alongshore variability is mainly due to the nutrient richness of the subsurface waters. The excess of nutrients in the surface layer triggers the offshore extension of the chlorophyll-rich coastal band. It also results in the increase of surface nutrients concentration and in the lack of correlation between the intraseasonal variability of wind forcing and chlorophyll. Other mechanisms have an impact on the width of the rich coastal band : mesoscale dynamics induced offshore-onshore exchanges export offshore rich coastal waters. An idealized coastal upwelling ecosystem model was built to investigate the impact of mesoscale dynamics. The introduced parametrization of the onshore subsurface flow permits a realistic representation of the circulation, with a surface coastal jet and a undercurrent along the slope. The comparison of an eddying simulation with a non-eddying simulation having the same mean circulation shows that the width of the rich coastal band is increased by the presence of mesoscale circulation and that the global phytoplankton content is reduced. This decrease is at least partially due to the downward phytoplankton export by the filaments of negative velocity associated with the mesoscale dynamics.
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Contributor : Cyril Lathuilière <>
Submitted on : Tuesday, April 13, 2010 - 9:25:12 AM
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  • HAL Id : tel-00472688, version 1


Cyril Lathuilière. Echanges côtes-large et propriétés biogéochimiques dans les régions d'upwelling de bord Est. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨tel-00472688⟩



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