Light scattering observations in the northwest African upwelling region

Abstract

Observations of suspended matter by a light scattering technique in the northwest African upwelling area are described. The distributions are compared with the temperature distributions and interpreted by considering upwelling dynamics. The observations suggest that there was upwelling over the shelf and slope, that the upwelling system reached depths of 300 to 400 m over the slope, and that the system prevailed to about 130 km from the coast. The scattering distributions indicate the frontal character of the upwelling zone and that this zone moved seawards during an upwelling event. Over the shelf and slope there was a turbid bottom boundary layer, generated on the shelf by the southgoing wind-driven current and related on the slope to the poleward undercurrent. At least part of the suspended matter in the layer was supplied by settling from the surface layer. The mean currents could not cause bottom erosion.