Temporal variability of mass transport in the Canary Current

Abstract

Abstract The variability of the Canary Current is investigated using bimonthly expandable bathythermograph sections from Gran Canaria Island to the African coast between November 1996 and September 1998. The geostrophic transport of the easternmost branch of the Canary Current is estimated by integrating the thermal wind equation using the layer of neutral density 27.3 (roughly 600 m depth) as the layer of no motion. The yearly average geostrophic transport of this branch of the Canary Current is 1.8±1.4×10 9 kg s −1 southward. Approximately half of the transport flows through the channel between the islands of Gran Canaria and Fuerteventura, and the other half through the channel between Fuerteventura and the African coast. The total southward geostrophic transport shows significant seasonal variability, ranging from 1.2±0.3×10 9 kg s −1 in May to 2.6±0.1×10 9 kg s −1 in January, although November is the only month with considerable differences in geostrophic transport between 1996 and 1997. There is seasonal northward transport in both channels, during May in the Gran Canaria–Fuerteventura channel and during November in the Fuerteventura–African coast channel. This seasonal pattern is probably linked to autumn weakening of upwelling in the Canary Islands area and the offshore diversion of this flow at Cape Ghir.