| Project/Area Number |
13650563
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
水工水理学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
YAGI Hiroshi Tokyo Institute of Technology, Graduate school of Science and Engineering, Associate Professor, 大学院・理工学研究科, 助教授 (80201820)
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| Co-Investigator(Kenkyū-buntansha) |
HINATA Hirobumi National Institute for Land and Infrastructure Management, Senior researcher, 国土技術政策総合研究所, 主任研究官 (70272680)
KANDA Manabu Tokyo Institute of Technology, Graduate school of Science and Engineering. Associate Professor, 大学院・理工学研究科, 助教授 (90234161)
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| Project Period (FY) |
2001 – 2002
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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2002: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2001: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Keywords | Nutrient salt / Kuroshio fluctuations / Coastal upwelling / Open coast / semi-enclosed bay / Middle layer intrusion / Field observation / Numerical experiment / 外洋水進入 / 東京湾 / 密度流 / 数値モデル / 季節変動 / 底層流入 / 黒潮 / 親潮 / 現地計測 / クロロフィルa / 基礎生産力 |
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| Research Abstract |
In order to estimate and understand the mechanism of nutrients flux from the outer ocean to the coastal region, two different types of coastal area were investigated. In the first case, field observations were carried out within the Kashima coastal region to understand the effect of the Kuroshio Current on the nutrient salt distribution and primary production along the Kashima open coast. The observations showed there is a surge in the concentration of nutrient salts, the duration of the surge, at one or two months. Comparison with observations made in previous periods showed that there are two kinds of response of the Kashima coastal current system to the approaching Kuroshio. When the approaching Kuroshio is not close to the coastal region, an anticlockwise gyre is induced off the Kashima coast and low-salinity and low-temperature water intrudes from the northern area (Jyoban coast) to the coastal region. When the approaching Kuroshio is close to the coastal region, high-nutrient water wells up from the offshore bottom layer. In the second case, numerical experiment were performed for Tokyo bay to understand the intrusion process of oceanic water into a semi-enclosed estuary. The simulation results showed that the oceanic water induction process involves transition between two kinds of flow structure : the normal estuary circulation type (two layers) and middle layer intrusion type (three layers). While the three layer structure is apparent, oceanic water intrudes into the middle layer of eastern part of Tokyo bay and coastal water at surface and bottom layer outflows through the western Dart of Tokyo bay. This agrees well with field observation. An annual analysis based on the numerical experiment results showed that the intensity and structure of oceanic water intrusion exhibits remarkable seasonal variation, hence intrusion in summer is stronger and the core of oceanic intrusion water is closer to the surface than that in winter.
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