Satellite observations of mesoscale eddies in the Gulfs of Tehuantepec and Papagayo (Eastern Tropical Pacific)

摘要

SeaWiFS high-resolution ocean-color images and AVHRR sea-surface temperature were obtained for the period from November 1998 to March 1999. Generation of mesoscale eddies was observed for the region between the Gulf of Tehuantepec and the Gulf of Papagayo (Tropical Pacific Ocean). Eighteen eddies with diameters ranging between 100 and 450km were identified; 14 originated in the Gulf of Tehuantepec and most were cyclonic. Our results show that the frequency of cyclonic eddy formation is higher than it has been reported and their lifetime can be longer. Using both ocean color images and daily temporal resolution, instead of sea-surface temperature alone, improved our ability to identify and follow the propagation of these eddies. The generation and fate of smaller cyclonic eddies around the periphery of the anticyclonic eddy indicate the importance of the onshore-offshore exchange of energy and biological material, which has not been considered previously. Three anticyclonic eddies were generated in the Gulf of Papagayo. These eddies have a common origin, and they travel along the main flux of the Costa Rica Coastal Current (CRCC), which later turns offshore and joins the North Equatorial Current. This behavior can be seen clearly on SeaWiFS images and suggests that the CRCC influences eddy propagation. Time series of chlorophyll-a concentration and SST were obtained from two points at Tehuantepec and two at Papagayo. Cross-correlation analysis confirms an inverse relationship between these variables, showing that a decrease in SST is followed by an increase in chlorophyll-a concentration values, indicating high growth and primary production rates.