Meander of the Kuroshio Front and Current Variability in the East China Sea

Abstract

To investigate the fluctuation of the Kuroshio front, moored current meters were deployed near the shelf break and on the continental slope in the East China Sea, northwest of Okinawa Island, during a period from 25 June to 22 July 1984. Two mooring arrays were deployed on the slope of about 800m water depth (under the Kuroshio), about 30km apart along the path of the Kuroshio. Another two arrays were set near the shelf break of about 300m water depth.
The fluctuation of current on the slope is found to have a predominant period of 11-14 days and a wave length of 300-350km, propagating toward the downstream direction of the Kuroshio with a phase velocity of about 30 cm sec^-1. When the Kuroshio front approaches the shelf break and the crest of the meander covers the mooring site, the current direction moves toward the downstream direction of the Kuroshio and the water temperature increases. On the other hand, when the trough of the meander covers the mooring site, the current direction changes offshoreward across the Kuroshio or in the upstream direction of the Kuroshio, and the water temperature decreases. Three-dimensional distributions of water temperature and salinity around the mooring site were observed with a CTD twice at 5.5 days intervals, which indicate the meanders of the front is about 180°C out of phase. This coincides with a period of 11-14 days obtained with the moored current meters. Wave lengths of the dominant meander of the front in the satellite thermal images were about 350km and 100-200km, which also coincides with results obtained with the moored current meters.