Variability of the circulation in the southern Huanghai Sea and East China Sea during the two investigative cruises in June 1999

摘要

On the basis of the hydrographic data obtained from June 17 to 25, 1999 on board R/V Eardo, Korea (hereafter "the second cruise"), the circulation in the southern Huanghai Sea and East China Sea is computed by using the modified inverse method. The comparison between the two computed results in the first cruise, which was carried out from June 4 to 19, 1999 on board R/V Xiangyanghong 14, China, and in the second cruise is made. The following results have been obtained. (1) Part of the Kuroshio flows northward through the eastern part of Section E, and its volume transport(VT) is about 6.2 x 10~6 m~3/s,and its maximum velocity is about 93 cm/s.This shows that most of the Kuroshio flows northward through the region east of Section E.The VT of the offshore branch of Taiwan Warm Current west of the Kuroshio through Section E is about 0.4 x 10~6 m~3/s. (2) There is the following variability between these two cruises, whose time difference is about two weeks: ① The position of the Kuroshio in the second cruise is slightly more east than that in the first cruise; ②The high-density water (HDW) with a cold water occurs in the region south of Cheju Island between 125°0′ and 127°E at Sections D and C. The circulation in the region of HDW is cyclonic. Comparing the position of HDW during the second cruise with that during the first cruise, it is found that its position in the second cruise moves slightly northward. (3) The cold and uniform mixing layer occurs in the layer from the 30m level to the bottom of the middle part of Section A and in the layer from the 20 m level to the bottom of the middle part of Section B, respectively. They are both the southern part of the Huanghai Sea Cold Water Mass (HSCWM). (4) There are higher temperature and lower density with a weaker anticyclonic circulation in the southwestern part of the computed region.Its center is located at the westernmost point of Section E.