Spatial and temporal trends of sea surface temperature in the northwest African region

The timing and structure of sea surface temperature (SST) changes were inve stigated using data from the continental shelf of the northwest African reg ion and from coastal stations in Mauritania. Empirical Orthogonal Function analysis of the data revealed differences between northern regions with per manent upwelling, and southern regions where the upwelling is seasonal. It is then hypothesized that shifts in the onset and duration of upwelling may be occurring. Furthermore, the Mauritanian shelf area, a transition zone b etween the northern and southern regions, appears to go through a series of cooling and warming trends, which seem to be part of a long-term process a ffecting the northwest African coast. In this regard. it is shown that ther e is a strong relationship between SST at 18-20 degrees N latitude and the Coastal Upwelling Index computed at a coastal station. This approach may al low for adequate predictions of oceanographic processes over the Mauritania n shelf, and probably the northwest African region, from coastal stations, as has been proven in other upwelling systems such as the California system . (C) Elsevier, Paris / Ifremer / Cnrs / Ird.