NUTRIENTS, CHLOROPHYLL AND OXYGEN RELATIONSHIPS IN THE SURFACE-LAYERS AT THE AGULHAS RETROFLECTION
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During the Agulhas Retroflection cruise (ARC) in November-December 1983, data were obtained on the distribution of nutrients, oxygen and chlorophyll a in the area between the south of Africa and the Subtropical Convergence. Several frontal systems were observed, which were distinguished by enhanced sea surface chlorophyll a and fluorescence values. Subsurface waters could be differentiated by means of nutrient and chlorophyll concentrations; in particular, the lowest concentrations of all parameters were found in the zone between the Agulhas and Agulhas Return currents, while the Subtropical Convergence zone exhibited the highest nutrient levels. Agulhas Current water showed a substantial oxygen minimum layer, derived from the tropical surface water of the Indian Ocean, at a depth of 50-200 m. This water penetrated under certain conditions as a lobe almost unchanged as far west as 16E during the cruise period; it can be found at least as far west as 13E at 34S. Detached Agulhas rings showed this feature, which may be a useful index of the penetration of Indian Ocean thermocline water into the Atlantic. Nutrient concentrations in the rings varied depending on the degree of mixing between water of Indian and Atlantic Ocean origin. 1987.
