Satellite observations and numerical simulation of the upwelling induced by the meandering of the Kuroshio current over the continental margin

The objective of this study is to investigate the characteristics of the Kuroshio current over the continental margin in the southern East China Sea using AVHRR images from NOAA satellites and a three-dimensional semi-spectral primitive equation model. In the satellite images, there are significant seasonal variations in the meandering of the Kuroshio and upwelling North of Taiwan. The Kuroshio intrudes onto the continental slope and shelf north of Taiwan in the winter, but it migrates offshore toward the deeper water in the summer. Upwelling is associated with the path of the meandering Kuroshio and is always located at the western side of the Kuroshio. In the numerical simulation, the main axis of the jet water intrudes onto the continental slope during the north monsoon with the steady onshore Ekman drift. Some subsurface water also intrudes onto the continental slope and shelf before rejoining the main stream. In the summer, surface water in the meandering jet migrates offshore under the influence of the south monsoon. The south monsoon induces the steady offshore Ekman drift and also intrusion of subsurface water onto the continental slope and shelf. The numerical simulations suggest that the path of the meandering Kuroshio and Kuroshio surface and subsurface waters north of Taiwan are influenced by both topographic effects and the steady Ekman drift. These intrusion processes induce momentum and mass exchanges in the East China Sea. The numerical simulations suggest that anticyclonic eddies formed in this region tend to propagate with a clockwise migration path. During the 90-day simulation, the eddy travels about 234 km with a mean velocity of about 3.0 cm/s. The anticyclonic eddy decays through its lifetime and loses water during its migration onto the continental slope. Moreover, the anticyclonic eddy propagating over the continental margin induces upwelling and exchanges of momentum and water mass. These results suggest that the topographic effects in the upwelling regions north off Taiwan play a prominent role in meandering Kuroshio and eddies.