2001 Fiscal Year Final Research Report Summary
Studies on the water-mass formation and temperature determination in the Kuroshio and Kuroshio Extension regions
| Project/Area Number |
11440138
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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 | The University of Tokyo |
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Principal Investigator |
YASUDA Ichiro Graduate School of Science, The University of Tokyo, Associate Professor, 大学院・理学系研究科, 助教授 (80270792)
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| Co-Investigator(Kenkyū-buntansha) |
MASUMOTO Yukio Graduate School of Science, The University of Tokyo, Research Associate, 大学院・理学系研究科, 助手 (60222436)
HIBIYA Toshiyuki Graduate School of Science, The University of Tokyo, Professor, 大学院・理学系研究科, 教授 (80192714)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Kuroshio / Kuroshio Extension / ocean current / water mass / physical oceanography / oceanography / air-sea interaction |
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| Research Abstract |
We introduced Lowered Acoustic Doppler Current Profiler (LADCP) by this grant. We developed a data processing algorithm for LADCP with CTD data that is as accurate as a few cm/sec. With this LADCP, we performed a series of observations in the northwestern Pacific in July 1999, August-September 1999, February-March 2000, October-November 2000, January-February 2001, in which we obtained total observations amounted to be over 180days and over 450 stations of LADCP data in two years. This intensive and extensive LADCP observations are remarkable for the world oceanographic community. Using these LADCP and CTD data, we developed a analysis method for estimating adjusted geostrophic velocity and vertical mixing coefficients. We applied these new methods to quantifying surface and subsurface circulations to produce a large number of results and publications. We developed a analysis method of vertical velocity assuming quasi-geostrophic dynamics, and we obtained results of large vertical velocities along isopycnal surface and surface-subsurface interaction and subduction along the Kuroshio Extension. We also performed historical data analyzes; in early 20th century the interdecadal SST variations occurred in the Kuroshio Extension regions as in late half. With historical data combined with bulk mixed layer models, we clarified the importance of heat transport by the Kuroshio and Kuroshio Extension on the determination of SST. Regime shifts of mixed layer depths and temperature were detected and the change of mixed layer depth a few years preceded the SST shift. The shifts in late 1980s are suggested to be due to the combinations of shifts in mixed layer and heat transport. From oceanic general circulation models, heat transport by the Kuroshio is also suggested to be crucial for temperature.
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