Circulation of Intermediate and Deep Waters in the Philippine Sea |
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| Authors: | Ikuo Kaneko Yasushi Takatsuki Hitomi Kamiya |
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| Institution: | (1) Oceanographic Research Department, Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305-0052, Japan;(2) Climate and Oceanographic Department, Japan Meteorological Agency, 1-3-4 Ohtemachi, Chiyoda-ku, Tokyo 100-8122, Japan |
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| Abstract: | The circulation of intermediate and deep waters in the Philippine Sea west of the Izu-Ogasawara-Mariana-Yap Ridge is estimated
with use of an inverse model applied to the World Ocean Circulation Experiment (WOCE) Hydrographic Program data set. Above
1500 m depth, the subtropical gyre is dominant, but the circulation is split in small cells below the thermocline, causing
multiple zonal inflows of intermediate waters toward the western boundary. The inflows along 20°N and 26°N carry the North
Pacific Intermediate Water (NPIW) of 11 × 109 kg s−1 in total, at the density range of 26.5σθ–36.7σ2 (approximately 500–1500 m depths), 8 × 109 kg s−1 of the NPIW circulate within the subtropical gyre, whereas the rest is conveyed to the tropics and the South China Sea. The
inflow south of 15°N carries the Tropical Salinity Minimum water of 35 × 109 kg s−1, nearly half of which return to the east through a narrow undercurrent at 15–17°N, and the rest is transported into the lower
part of the North Equatorial Countercurrent. Below 1500 m depth, the deep circulation regime is anti-cyclonic. At the density
range of 36.7σ2, – 45.845σ4 (approximately 1500–3500 m depths), deep waters of 17 × 109 kg s−1 flow northward, and three quarters of them return to the east at 16–24°N. The remainder flows further north of 24°N, then
turns eastward out of the Philippine Sea, together with a small amount of subarctic-origin North Pacific Deep Water (NPDW)
which enters the Philippine Sea through the gap between the Izu Ridge and Ogasawara Ridge. The full-depth structure and transportation
of the Kuroshio in total and net are also examined. It is suggested that low potential vorticity of the Subtropical Mode Water
is useful for distinguishing the net Kuroshio flow from recirculation flows.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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| Keywords: | WOCE inverse method intermediate water deep water |
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