Diapycnal transport from bottom boundary layers to interior waters over sloping topography

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H01970
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Kyushu University
• Principal Investigator: Endoh Takahiro 九州大学, 応用力学研究所, 准教授 (10422362)
• Co-Investigator(Kenkyū-buntansha): 松村 義正 東京大学, 大気海洋研究所, 助教 (70631399)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 乱流混合 / 海底斜面 / Tidal straining / 乱流微細構造観測 / 三次元非静水圧モデル

Outline of Final Research Achievements

Using microstructure data obtained over the continental shelf of the East China Sea, we verified that vertical turbulent flux of buoyancy in the bottom boundary layer (BBL) can be estimated as a product of background density gradient and vertical eddy diffusivity calculated from (1) the dissipation rate of turbulent kinetic energy (TKE) measured with a microstructure profiler deployed from a ship and/or (2) the production rate of TKE measured with an acoustic Doppler current profiler deployed on the seabed. By coupling an online particle tracking framework with a three-dimensional non-hydrostatic model, “kinaco”, we demonstrated that the mixing asymmetry due to tidal straining generates the transport of sediment particles lifted from the seabed, which is directed towards the inner continental shelf regardless of the size of particles.

Free Research Field

海洋物理学

Academic Significance and Societal Importance of the Research Achievements

陸棚斜面域の海底混合層上端を境として生じる、乱流運動がもたらす密度フラックスの収束・発散によって、深いところにある密度の大きい水塊が、海底混合層内を斜面沿いに陸棚上へと移動しながら密度躍層へと湧昇し、等密度面に沿って沖側へ戻るという二次元的な輸送過程が生じ得る。本研究で得られた成果を端緒として、海底斜面と海底混合層との組み合わせによる二次元循環の存在が明らかになれば、陸棚斜面域にとどまらず、全球的な深層海洋大循環まで含めた、新しい物質循環研究の展開に大きく貢献するものと期待される。