2025/07/15 by Xiangpeng Wang, Yan Du, Xiaoming Zhai +2 · 1 citation
Earth and Planetary Sciences · Environmental Science · #Geological and Geophysical Studies #Oceanographic and Atmospheric Processes #Methane Hydrates and Related Phenomena
paper · doi:10.1175/jpo-d-24-0152.1
Abstract The Kuroshio anticyclonic eddy-shedding event occurs nearly every winter in the northeastern South China Sea (SCS). Between 1993 and 2023, 27 prominent Kuroshio-shed anticyclonic eddies were identified based on satellite altimetry data. These eddies propagated southwestward along the continental slope and typically dissipated near the Xisha Islands in spring, with an average lifespan of approximately 89 days. Notably, three exceptionally strong and long-lived eddies were observed in 2010, 2017, and 2021, each persisting for more than 180 days. Unlike the regular eddies that dissipated upon encountering the Xisha Islands, these long-lived eddies slightly moved eastward along the topography and reintensified during summer. Eddy–current interactions and eddy mergers were identified as the primary mechanisms driving their reintensification. Hydrographic observations revealed that the long-lived Kuroshio eddies evolved seasonally from surface-intensified to subsurface-intensified eddies, ultimately exhibiting a lens-shaped structure in the upper 300 m. The intense lens core was enclosed by a strong potential vorticity (PV) gradient, acting as a PV barrier that prevents water exchange between the eddy interior and its surroundings. Despite undergoing interactions that reintensified the eddy, the eddy core maintained its high-salinity and low-PV characteristics. Such intrinsic eddies may play an important role in local air–sea interactions, heat–salt balances, and biogeochemical processes. Significance Statement The Kuroshio intrusion and its associated anticyclonic eddy shedding are key dynamic processes in the northern South China Sea (SCS). This study examines the statistical characteristics of Kuroshio-shed anticyclonic eddies, focusing on the evolution of those that are strong and long lived. Most Kuroshio eddies form in winter and dissipate by spring, but some strong eddies reintensify east of Xisha Islands during summer, allowing persistence into autumn. Eddy–current and eddy–eddy interactions are primary mechanisms driving their reintensification. The reintensified eddies retain Kuroshio water characteristics within their cores due to the potential vorticity (PV) barrier, while the merging water wraps around the eddy periphery. This study highlights the evolution of Kuroshio eddies in the SCS and their interactions with the surrounding environment.