OCCURRENCE OF ANTICYCLONIC EDDIES ON THE PRINCE-EDWARD PLATEAU (SOUTHERN-OCEAN) - EFFECTS ON PHYTOPLANKTON BIOMASS AND PRODUCTION

Dimensional analysis suggests that mesoscale eddies observed at the Prince Edward Islands (47°S, 38°E) are unlikely to be the result of an island wake vortex shedding process. The analysis shows that appropriate conditions can exist for the formation of closed streamline, anticyclonic eddies (Taylor columns) over the plateau. Hydrographic observations on six surveys in the area show the repeated presence of anticyclonic eddies in the vicinity of the islands. These eddies appear to have some characteristics that are consistent with Taylor column phenomena, but the spatial resolution of the hydrographic data is not sufficient to draw conclusive results. Dense phytoplankton blooms are repeatedly found between the islands. A mechanism explaining these blooms in terms of the stability of the surface mixed layer and the availability of reduced forms of nitrogen is proposed. It is suggested that both water-column stability and available nutrient concentrations are locally enhanced by run-off retained by the eddy field. © 1990.