| Summary: | I Encuentro de la Oceanografía Física Española (EOF), 13-15 de octubre 2010, Barcelona The region south of the Cape Verde Frontal Zone (CVFZ) is known as the “shadow zone” of the North Atlantic Subtropical Gyre, as it is not reached by central waters of northern origin and the dominant flow pattern is thought to be recirculation around the Guinea Dome. North of the front, newly subducted North Atlantic Central Water (NACW) flows southwestward within the eastern boundary current system before turning west as the North Equatorial Current, while south of the front quasi‐stagnant and old South Atlantic Central Water (SACW) occupies the upper thermocline. T/S diagrams from historical observations east of Cape Verde Islands actually show the co‐existence of this older SACW with a fresher and more oxygenated variety at subsurface depths, between 150 and 300 m. This new variety has characteristics much closer to tropical waters southwest of the Guinea Dome. During the CANOA08 cruise, carried out in November 2008 on board the R/V Sarmiento de Gamboa, we took Conductivity‐Temperature‐Depth‐Oxygen and Lowered‐Acoustic Doppler Current Profiler measurements in the CVFZ region which show the northward penetration of this relatively fresh and oxygenated SACW variety. We use these data, together with data from a transatlantic section along 7.5°N obtained during a May 2010 R/V Hesperides cruise, to show that the western tropical Atlantic is the probable origin of this SACW variety, likely advected by the North Equatorial Counter Current into the eastern Tropical North Atlantic. This water mass shows oxygen values higher than the predominant waters in the shadow zone, so its penetration seems to be an essential mechanism for tropical ventilation and oxygen supply to the region Peer Reviewed
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