The physical structure of an upwelling filament off the North-West African coast during August 1993

Abstract

Recent work in the Canary Current upwelling system highlights the role of previously uninvestigated filament structures. A filament located near 27°N in summer 1993 extended 150 km offshore with a width of ∼20 km and surface temperature anomaly up to 2°C. The cool temperature signal was restricted to a shallow surface layer, and the filament was entrained around a large cyclonic eddy. Offshore transport in the filament, in excess of 1 Sv, may be a major influence in dispersal of material originating in the region of active coastal upwelling. The location of the filament studied appears repeatable from year to year, suggestive of a strong relation with the topographically trapped eddy, which was situated downstream of a lateral ridge between the Canary Islands and the African coast.