Water property and current distributions along the WHP-P9 section (137°-142°E) in the western North Pacific

The Japan Meteorological Agency carried out full-depth, high-resolution hydrographic measurements in July-August 1994 along the 137°-142°E line as a contribution to the World Ocean Circulation Experiment. The line spans the subtropical and tropical regions of the western North Pacific with a full set of water mass and current distributions. At 28°N to the south of the Kuroshio recirculation, there exists an eastward current distinct from the currents associated with the subtropical fronts. The eastward current is characterized by the meridional thermal gradient extending down to 1500-m depth. Deep silicate has a meridional boundary at 25°N, forming two cores of the maximum to the north and south of the boundary. The northern core centered at 28°N is meridionally coincident with other property extrema, indicating an inflow from the Northwest Pacific Basin down to 2000-m depth. The southern core centered at 16°N suggests another westward inflow from the East Mariana Basin to the West Mariana Basin. A broad isopycnal depression at middepths and bottom water properties over the Shikoku and West Mariana Basins indicate a near-bottom circulation along which the inflow water through the Yap-Mariana Junction at 12°N fills the West Mariana Basin and then spreads to the Shikoku Basin and Philippine Basin successively. A part of the bottom water from the South Pacific bifurcates around the Yap-Mariana Junction and enters the West Caroline Basin via the Yap Trench. This supports another path of deep water inflow to the Philippine Basin from the southernmost channel at 4000-m depth.