A note on the deep circulation in the area east of Taiwan and the Philippines

The deep water (1000–3000 m) circulation in the area east of Taiwan and the Philippines has been little studied. Moriyasu (1972) and Reid (1981) discussed the 3000 db surface (3000/1200 db) and 2000 db surface (2000/3500 db) circulations of the Philippine Sea Basin, respectively. They both showed that there may be a northward current close to the western margin of the Sea Basin. Recent analyses of two sets of deep sea hydrographic data yielded quite different results, i. e., at deep waters in the area east of Taiwan and the Philippines southward countercurrents flow under the upper northward currents. The possible causative mechanism of these southward deep countercurrents is the blocking effects of the submarine ridge east of Suao and of the Ryukyu Islands Shelf on the northward flowing upper currents. The above-mentioned preliminary deductions were wholely based on consideration of the relative geostrophic current and calculation, though the reference surface (3500 db) was very deep. It is suggested that direct measurements of the deep currents in the study area are needed to verify these results. Contribution No. 1750 from the Institute of Oceanology, Academia Sinica. This paper was presented at the PRC/USA Symposium on Western Pacific Air-Sea Interaction (Nov., 1988, Beijing). This project was supported by the National Natural Science Foundation of China.