DISTINCT YEAR-TO-YEAR PARTICLE-FLUX VARIATIONS OFF CAPE-BLANC DURING 1988-1991 - RELATION TO DELTA-O-18-DEDUCED SEA-SURFACE TEMPERATURES AND TRADE WINDS

Particle fluxes measured from 1988 to 1991 adjacent to a coastal upwel ling site off Cape Blanc showed significant interannual variability of fluxes and sea-surface temperatures (SST) deduced from stable oxygen isotope analysis of the planktonic foraminifera Globigerinoides ruber and, partly, of the pteropod Limacina inflata. For the duration of the study period, a decrease in the seasonality of SST's was observed, as well as a significant decrease in the average annual SST from 24.4 de grees to 20.8 degrees C. This cooling trend was mainly the effect of a drastic decrease in the summer to fall SST (from 27.2 degrees to 21.8 degrees C). In comparison, the winter-spring SST decreased only sligh tly from 20.3 degrees in 1988 to 19.8 degrees C in 1991. Concomitantly , we measured decreasing annual total, carbonate, biogenic opal and li thogenic fluxes and, in contrast, increasing marine organic carbon flu xes. During 1991, when cold SST's prevailed and the trade winds were r ather high throughout, annual biogenic and lithogenic fluxes (except o rganic carbon) were lower by approximately a factor of two compared to the other years. Colder SST's, generally corresponding to stronger tr ade winds and upwelling intensity, did not result in increased biogeni c opal and lithogenic matter sedimentation; but higher marine organic carbon fluxes were recorded. Decreasing summer-fall SST from 1988 to 1 991 coincided with decreased carbonate sedimentation maxima which gene rally occurred during the warm summer season. In the summer of 1989, w hen SST's were the highest of the four-year sampling period and upwell ing was less intense due to weak spring-summer trades, a large sedimen tation pulse of pteropod shells was observed. Our data set does not ye t provide conclusive evidence that the observed year-to-year flux and SST variations represent larger-scale, periodically occurring climatic variations in the eastern Atlantic but it offers insight into the pre vailing large variability in biochemical cycles and processes in the e astern Atlantic.