Mesoscale eddies in the northeastern Pacific tropical-subtropical transition zone: Statistical characterization from satellite altimetry
Résumé
Mesoscale eddies in the northeastern Pacific tropical-subtropical transition zone (16°N-30°N; 130°W-102°W) are analyzed using nearly 18 years of satellite altimetry and an automated eddy-identification algorithm. Eddies that lasted more than 10 weeks are described based on the analysis of 465 anticyclonic and 529 cyclonic eddy trajectories. We found three near-coastal eddy-prolific areas: (1) Punta Eugenia, (2) Cabo San Lucas, and (3) Cabo Corrientes. These three areas are located in places where the coastal morphology changes abruptly and strong surface current intensification occurs at some phase of the seasonal cycle. Although mesoscale eddies in these areas have been previously reported, this study provides their first statistically supported characterization. Punta Eugenia showed the highest eddy production (with more cyclones generated), followed by Cabo Corrientes (also with more cyclones) and Cabo San Lucas (with more anticyclones). Cabo Corrientes eddies showed the highest mean values in propagation speed, swirling speed and eddy kinetic energy, whereas Punta Eugenia eddies showed the lowest values. Cyclonic eddies increased their distance traveled and duration from south to north; in contrast anticyclonic eddies increased from north to south. In average, anticyclones tend to travel faster than cyclones in all the subregions. These long-lived eddies were mainly nonlinear and therefore can redistribute coastal waters relatively far into the open ocean. The peaks in the seasonal signal of eddy generation can be associated with the peaks in the strength of the offshore currents and/or in the Coastal Upwelling Index. No clear relationship could be established between El Niño events and eddy generation.
Origine : Fichiers éditeurs autorisés sur une archive ouverte
Loading...