66 / 2023-07-26 15:31:14

Spatiotemporal Variation of Warm Eddies in the South China Sea during 1993–2019

warm eddy; South China Sea; spatiotemporal variation; Topographic Position Index

Based on the absolute dynamic topography data from the Copernicus Marine Environment Monitoring Service, this paper applies the Topographic Position Index to develop a new approach for mapping the warm eddies in the South China Sea (SCS). The results show that warm eddies are active in the deep basin of SCS, and the five selected parameters (number or frequency, lifetime, kinetic energy, amplitude, and area or radius) of warm eddies have a similar temporal variation and a similar spatial distribution pattern. (1) As for monthly variations, warm eddies are active in late spring and most active in summer. (2) The El Niño–Southern Oscillation had a strong impact on the annual variations of warm eddies in the SCS before 2013, resulting in a significant transition of inter-annual variations of these five parameters in around 2004. After 2013, most of these five parameters had a minimum in 2015 and a maximum in 2017. (3) The eddy activities in the SCS are significantly influenced by the monsoon wind and the western boundary current like Kuroshio. Therefore, the areas southwest of Taiwan Island and east of Vietnam are the two areas where the warm eddies are most active, with much larger eddy kinetic energy and much higher eddy amplitude.