Submesoscale Eddies in the South China Sea

Submesoscale eddies are often seen in high‐resolution satellite‐derived ocean color images. To efficiently identify these eddies from surface chlorophyll data, here, we develop an automatic submesoscale eddy detection method and apply it to the South China Sea. The detected submesoscale eddies are found to have a radius of 13 ± 5 km and an aspect ratio of 0.5 ± 0.2, with a notable predominance of cyclones. Further investigation reveals that the surface structure of these eddies displays a unique “cat's‐eye” pattern, and the eddies become more circular with increasing eddy radius. Submesoscale eddies can strongly regulate surface chlorophyll via horizontal advection while they have less coherent signatures in sea surface temperature. These findings may help to improve submesoscale parameterizations in Earth system models. Plain Language Summary Ubiquitous ocean eddies play a crucial role in the upper ocean dynamics. Using high‐resolution satellite remote sensing data, we have developed an automatic method to detect small elliptical eddies in the SCS over a 10‐year period. The results show that these “submesoscale” eddies of the order of 10 km appear to have a unique “cat's‐eye” structure with significant effect on the surface tracer distribution. This study, therefore, improves our understanding of oceanic submesoscale dynamics and contributes to parameterizing the impact of submesoscale eddies in climate and ocean models. Key Points Submesoscale eddies are detected automatically from ocean color data and are analyzed statistically in the South China Sea The surface structure of submesoscale eddies shows the classical “cat's‐eye” pattern Submesoscale eddies can significantly modulate surface tracer distribution