New insights in the French Guiana continental shelf circulation and its relation to the North Brazil Current retroflection

[1] Moored current measurements carried out from 6 October 2003 to 18 February 2004 over the French Guiana continental shelf are presented. Two contrasted situations have been evidenced in which the currents were either weak and oscillating during the first period ( from October to early December) or strong and northwestward during the rest of the survey. Further analysis of these measurements in light of Moderate Resolution Imaging Spectroradiometer satellite images have revealed that these situations are mainly due to the motion of an outer shelf mesoscale feature: the North Brazil Current (NBC) retroflection. Two other main results have also been evidenced in this survey: ( 1) When the NBC retroflection occurs northwestward of the French Guiana continental shelf, part of the NBC climbs over the shelf slope and propagates to the inner shelf, and ( 2) the "Guyana current'' does not persist throughout the year at a 22 m depth and below. Finally, the location of the NBC retroflection has also a strong impact on the spread of the Amazon plume over the French Guiana continental shelf and is felt to have an influence on the nutrient supply in this region.