PHYTOPLANKTON PIGMENT DISTRIBUTION AND FRONTAL STRUCTURE IN THE SUBTROPICAL CONVERGENCE REGION SOUTH OF AFRICA

Satellite data from the Coastal Zone Colour Scanner (CZCS) and Advance d Very High Resolution Radiometer were examined to determine the relat ionship between the phytoplankton pigment distribution and sea surface temperature (SST) in the Subtropical Convergence (STC) region south o f Africa. The structure of the temperature fronts and their role in ph ytoplankton pigment distribution was explored. The multichannel sea su rface temperature (MCSST) data for 1981-1986 showed considerable inter annual variability in both the position the Agulhas retroflection and the extent of the Rossby wave in the Agulhas Return Current. Pronounce d interannual variation in pigment levels was found in the CZCS data f or early 1979, 1982 and 1983, with highest pigment levels in early 198 2. These greater pigment levels were shown to be a function of increas ed frontal intensity of the STC front rather than of the Agulhas front , or of SST per se: The principal interannual differences were found i n the region where a strong Agulhas front occurred to the north of the STC front. The Agulhas front appeared to play a role in limiting the spatial distribution of phytoplankton pigment. Time series of level-2 CZCS data supported the scenario of upstream Agulhas retroflection res ulting in a pronounced Rossby wave in the Agulhas Return Current, and increased phytoplankton pigment levels in the STC region. Copyright (C ) 1996 Elsevier Science Ltd