A quasi-synoptic interpretation of water mass distribution and circulation in the western North Pacific: I. Water mass distribution

摘要

With high-resolution conductivity-temperature-depth (CTD) observations conducted in Oct.-Nov. 2005, this study provides a detailed quasi-synoptic description of the North Pacific Tropic Water (NPTW), North Pacific Intermediate Water (NPIW) and Antarctic Intermediate Water (AAIW) in the western North Pacific. Some novel features are found. NPTW enters the western ocean with highest-salinity core off shore at 15o-18oN, and then splits to flow northward and southward along the western boundary. Its salinity decreases and density increases outside the core region. NPIW spreads westward north of 15oN with lowest salinity off shore at 21oN, but mainly hugs the Mindanao coast south of 12oN. It shoals and thins toward the south, with salinity increasing and density decreasing. AAIW extends to higher latitude off shore than that in shore, and it is traced as a salinity minimum to only 10°N at 130°E. Most of the South Pacific waters turn northeastward rather than directly flow northward upon reaching to the Mindanao coast, indicating the eastward shift of the Mindanao Undercurrent (MUC).