persistently found on the shelf by Uda and Kishi [1974], Fan [1980], Liu et al. [1992], etc. This cold water was formed by the subsurface Kuroshio water and could be related to the intrusion of Kuroshio Current [Chern and Wang, 1989].
In addition to the spatial structure, the circulation pattern generated by the collision of Kuroshio with the continental shelf northeast of Taiwan also changes in time. Long-term GEK measurements reveal a seasonal shift in the position of Kuroshio axis northeast of Taiwan [Sun, 1987] which appears to migrate shoreward in fall and winter and seaward in spring and summer. This seasonal migration is collaborated with current meter observations that show an on-shelf intrusion of Kuroshio about one month into the winter monsoon season, giving rise to shoreward displacement of Kuroshio [Tang and Yang, 1993]. Accompanying the intrusion is the disappearance of countercurrent in the upper ocean (＜150 m). As the northeasterly wind collapses in spring, the on-shelf intrusion of Kuroshio ceases [Chuang et al., 1994].Obviously, the on-shelf intrusion of Kuroshio, branch current, countercurrent, and the uplifted of Kuroshio subsurface water are all flow features important in bringing about a vigorous mixing between the continental shelf water and the Kuroshio [Hsueh, 1996]. A systematic measurement of current is required.
In order to study the spatial distribution of current velocity along the shelf break of southern boundary of ECS, a systematic survey by using the Ship-board Acoustic Doppler Current Profiler (Sb-ADCP) was performed to map the flow pattern northeast of Taiwan. The mapping experiment was performed twice, in summer and winter, respectively. A phase averaging method was applied to eliminate affect of M2 tidal current which dominates in high frequency variation in this area. The obtained current velocity is described in the next section.
