Variations of Western Boundary of the Kuroshio in the East China Sea

Abstract

Studying on the temporal and spatial variations of the western boundary of the Kuroshio in the East China Sea (KECS) will help to further understand the interaction between Kuroshio water and East China Sea shelf water. In this paper, the temperature-salinity (T-S) scatter diagram statistical analytic method was improved to analyze the western boundary of the KECS; the temporal and spatial variations of the western boundary were manifested by using the MATLAB computer program. The following main results have been obtained. (1) The western boundary shows varying degree of convexity to the continental shelf area or concavity to the Kuroshio in different locations. (2) From the entrance to the exit, it is mainly in the northeast of Taiwan and the southwest of Kyushu that the western boundary bulges to the shelf area greatly above 100m depth, compared with the middle of the KECS from 100m to 200m depth. (3) If the convexity to the shelf area is defined as peak and the concavity to the Kuroshio is defined as valley, the western boundary appears peak and valley alternately from the surface to 200m depth. Alternate peak and valley changes greatly in different seasons above 100m depth, but changes little from 100m to 200m depth. (4) The spatial variations of the western boundary in spring and autumn are more dramatic than that in winter and summer, for there are eight depth layers with peak or valley in spring and autumn from the surface to 200m depth, in contrast to seven in winter and summer. (5) From winter to autumn, in terms of the surface, latitudes reached by the western boundary in the middle of the KECS (125.5°E) and southwest of Kyushu (128.5°E) changes little, respectively around 28.0°N and 31.0°N; but changes greatly in the northeast of Taiwan (122.5°E), respectively 26.4°N, 25.8°N, 25.3°N and 26.3°N in four seasons.