A preliminary study on the intermediate water masses in the tropical West Pacific

Based on the CTD data of China's first WOCE cruise in winter of 1991, and those of the first and second Chinese TOGA cruises in the winters of 1985 and 1986, we apply the classical method of T-S diagram analysis to identify intermediate water masses in the tropical West Pacific and study their distribution feature. Results of these analyses show that there are mainly two kinds of intermediate water masses,namely, the South Pacific Intermediate Water (SPIW) and the North Pacific Intermediate Water (NPIW) in the tropical West Pacific. The NPIW extends north to south with its southern boundary generally at about 8°N. However, it is westwards intensified near the coast of Mindanao Island where it extends further south to about 5°N with more distinctive characteristics of low salinity and temperature. The SPIW extends from south to north with its northern boundary at about 12°N. In the tonal area between 0° and 4°N various intermediate waters interact. The analysis also shows the existence of interannual variations of NPIW in the tropical West Pacific.