Results of the UNDP (SF)/FAO regional fisheries survey in West Africa. Report no. 4. T/S relationship in the Canary Current area

Abstract

Based on historical oceanographic data supplied by the National Oceanographic Data Center (NODC), Washington, D.C., USA, temperature salinity (T/S) diagrams were drawn for a large number of one-degree squares within marsden Squares (MS) 074, 038 and the northern half of MS 002. The shelf area of these squares was the area of the Regional Fisheries Survey activities in 1969 and 1970. The aim of the work is to illustrate the different characteristics of the water in the area. It is shown, in a set of diagrams, that the northern part of MS 074 contains nearly pure North Atlantic Central Water (NACW), except for the surface layer, where the characteristics change with season. In the upwelling area of Senegambia, during the upwelling season, the water is of a South Atlantic Central Water (SACW) and NACW mixed type, while in the offshore area it is nearly pure NACW. In the southern part of MS 074 and the northern part of MS 038, the subsurface water is a mixture of NACW and SACW, which changes into pure SACW southwards, but remains a mixture in medium depths. The SACW is always superimposed on the NACW. Inshore, the water mass changes with season. During the rainy season this is Liberian surface water of low salinity and high temperature. In MS 002, to the south, offshore, the subsurface water becomes pure SACW, which in deep parts overlays the Antarctic Water. Inshore at the surface, the water is desalinated during the rainy season. The Liberian surface water spreads over the whole of MS 002, nearly 1000 miles offshore.