How does the Natuna Cyclonic Eddy form in the Southern South China Sea, and what are its implications?

Abstract

This study investigates the Natuna Cyclonic Eddy (NCE) in the South China Sea, focusing on its formation processes, circulation characteristics, and impact on essential oceanographic parameters such as sea surface temperature (SST), chlorophyll-a concentration (CHL), and sea level anomaly (SLA). Through an analysis of an extensive 11-year dataset derived from satellite observations and ocean models, we identify that the NCE is primarily formed through the interaction between the Vietnam Coastal Jet and the sea topography of the Natuna Islands region. With its cyclonic circulation reaching maximum speeds of 0.6 m/s, the NCE promotes the vertical transfer of nutrients from deeper layers to the surface, thus boosting biological productivity in the surrounding waters. Additionally, our results indicate that the variability of the NCE is notably influenced by both annual and semi-annual cycles, as well as the El Niño-Southern Oscillation (ENSO); specifically, La Niña events result in a more intense NCE compared to conditions during El Niño. These findings are vital for effectively managing fishery resources and conserving marine ecosystems within the area.