| Project/Area Number |
13440138
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
SUGA Toshio TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, ASSOCIATE PROFESSOR, 大学院・理学研究科, 助教授 (70211977)
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| Co-Investigator(Kenkyū-buntansha) |
HANAWA Kimio TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, PROFESSOR, 大学院・理学研究科, 教授 (40142921)
KIZU Shoichi TOHOKU UNIVERSITY, GRADUATE SCHOOL OF SCIENCE, ASSOCIATE PROFESSOR, 大学院・理学研究科, 助教授 (40241517)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥8,100,000 (Direct Cost: ¥8,100,000)
Fiscal Year 2003: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2002: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Keywords | subduction / winter mixed layer / mode waters / potential vorticity / subtropical front / barrier layer / mesoscale eddy / Argo / 北太平洋亜熱帯循環 / 水塊 / 等密度面平均気候値 / プロファイリングフロート / 海洋気候値データ |
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| Research Abstract |
Origins of waters observed along 137°E were estimated based on the available climatological data, the World Ocean Atlas, to outline waters composing the subtropical permanent pycnocline. The original high-resolution hydrographic climatology was then constructed and analyzed to identify the source regions of Subtropical Mode Water(STMW), Central Mode Water(CMW) and Eastern Subtropical Mode Water and to reveal their formation mechanism. One of noticeable findings is that the low potential vorticity of CMW is caused by small "cross-isopycnal flow" rather than large "lateral induction." It was also revealed that southwestward advection of STMW and CMW contribute to the formation of the subtropical fronts. The similar original climatology also revealed the source region and the advection path way of the dichothermal water in the subarctic pycnocline.
Quasi-Lagrangian observations of CMW for the periods over one and half years were successfully done using the profiling floats parking at isopycnal surfaces corresponding to the CMW cores. A one-dimensional mixed layer model of the Lagrangian-type was developed to simulate the subduction processes to be compared with the quasi-Lagrangian data. The effectiveness of the model was confirmed by simulating the formation of the dichothermal water successfully.
The intense hydrographic survey in the central North Pacific including the source region of CMW was conducted by R/V Hakuho-Maru to collect multi-variable synoptic data just after the late winter period during which the subduction of the mixed layer water to the permanent pycnocline occurs.
All the available Argo float data were analyzed to reveal that the thick mode waters are formed associated with the deep permanent pycnocline associated with anticyclonic eddies and that the barrier layers are formed associated with the subduction of high-salinity water in the southern subtropical gyre.
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