SHIP AND SATELLITE-OBSERVATIONS OF CHLOROPHYLL STOCKS IN INTERACTING CYCLONE-ANTICYCLONE EDDY PAIRS IN THE WESTERN GULF-OF-MEXICO

When anticyclonic eddies shed by the Loop Current of the Gulf of Mexico reach the western margin of the gulf, they influence the surface circulation over the continental slope and rise. Of particular interest is the generation of cyclone (cold-core)-anticyclone (warm-core) pairs when aging Loop Current eddies interact with the continental margin. In this paper we describe the physical and biological characteristics of these cyclone-anticyclone pairs. Our objective was to determine how eddy pairs affect the distribution of phytoplankton in the region and how satellite ocean color measurements are applicable to tracing of the eddies. We present shipboard data collected between 1980 and 1982 on the hydrography, chlorophyll stocks, and nutrient concentrations of eddy pairs in the western Gulf of Mexico and compare these data with coastal zone color scanner (CZCS) images collected during the time frame of the cruises. Surface pigment concentrations followed a seasonal cycle, with low concentrations (0.05-0.1 mg m-3)found within cyclones and anticyclones from April through early November and higher concentrations (>0.1 mg m-3) found in the winter. CZCS pigment concentrations were locally high in the flow confluence of cyclone-anticyclone pairs. The CZCS imagery shows that some cyclone-anticyclone geometries transport high-chlorophyll shelf water seaward at least 100-200 km off-shelf.