Identification and Feature Analysis of Submesoscale Eddies in the South China Sea and Adjacent Regions Based on Argos Drifters

Submesoscale eddies, serving as a link between mesoscale eddies and small-scale turbulence, have a significant impact on energy cascades and material transport in the ocean. To study the characteristics of submesoscale eddies in the South China Sea and adjacent regions, this study develops a method for identifying submesoscale eddies based on the geometric features of Lagrangian drifting trajectories. An analysis was conducted on the trajectories of 1 685 Argos drifters buoys that entered the study area between 2000 and 2022 as part of the Global Drifter Program. A total of 11 988 submesoscale eddies were identified, with an anticyclonic to cyclonic eddy ratio of approximately 5∶1. The radius and lifespan of these eddies are positively correlated, mostly within 3 km and 24 hours, respectively. Submesoscale eddies appear frequently in the northern South China Sea, decreasing southwestward along the continental slope from the northwest of the Luzon Strait. submesoscale cyclonic eddies are relatively more active in the southern coast of the Indo-China Peninsula. The seasonal variation of submesoscale eddies in the study area is evident, with higher activity in winter and summer and less in spring and autumn.