Observations of the Luzon Cold Eddy in the northeastern South China Sea in May 2017

Combining cruise observations, satellite altimeter and Argos drifter data in the northeastern South China Sea in the spring of 2017, this paper reports a Luzon Cold Eddy (LCE), which originated near the northwestern coast of Luzon Island. Then it migrated northwestward and was sampled by the cruise transect to the southwest of Taiwan Island. In the core of the LCE, the isotherm, isohaline and isopycnal all uplifted by approximately 100 m within the depth range of 150-300 m. The corresponding geostrophic currents were consistent with satellite altimeter results. In addition, a double-index was applied to study the dynamical process for the LCE evolution. The index reflects well the intraseasonal variability of eddies and the Kuroshio pathway in the spring of 2017. During the second half of April, the enhancement of the LCE was regulated by the velocity shear resulting from a large anticyclonic eddy east of the Luzon Strait. Taken together, the results of this study demonstrate a better understanding of the circulation and mesoscale patterns and a potential implication for water mass renewal in the northeastern South China Sea.