2019 Fiscal Year Final Research Report

Dynamical analysis of diapycnal mixing processes in the ocean toward the formulation of their accurate parameterizations

Planned Research

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Project Area	Ocean Mixing Processes: Impact on Biogeochemistry, Climate and Ecosystem
Project/Area Number	15H05824
Research Category	Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
Allocation Type	Single-year Grants
Review Section	Complex systems
Research Institution	The University of Tokyo
Principal Investigator	HIBIYA Toshiyuki 東京大学, 大学院理学系研究科(理学部), 教授 (80192714)
Co-Investigator(Kenkyū-buntansha)	吉川裕京都大学, 理学研究科, 准教授 (40346854) 田中祐希東京大学, 大学院理学系研究科(理学部), 助教 (80632380) 丹羽淑博東京大学, 大学院教育学研究科(教育学部), 特任准教授 (40345260)
Project Period (FY)	2015-06-29 – 2020-03-31
Keywords	内部重力波 / 潮汐流 / 海底地形 / 非線形相互作用 / 乱流パラメタリゼーション
Outline of Final Research Achievements	Existing parameterizations of turbulent mixing in the deep ocean especially over rough bathymetry still have plenty of room for improvement. In this study, we have made improvements on them based on various theoretical and numerical studies and confirmed their validity in terms of the comparison with the results of microstructure measurements which we carried out over the Izu-Ogasawara Ridge using VMP-5500 and/or VMP-X. Besides such improvement of the existing turbulent mixing parameterizations, we have successfully carried out microstructure measurements covering the whole Indonesian Seas, the results of which are expected to provide invaluable information toward the accurate prediction of global climate change. We have also proposed a new generation mechanism of Langmuir circulation based on the results of the numerical experiments that take into account the interaction between surface waves and wind-induced current in the sea surface layer.
Free Research Field	海洋物理学
Academic Significance and Societal Importance of the Research Achievements	本研究は、海洋物理学において最大の不確定要素として残されてきた海洋乱流の定量化に取り組んだ意欲的な研究である。本研究の成果である「海面から海底までシームレスにつながる乱流パラメタリゼーションの定式化」は、気候変動予測の精度の格段の向上に寄与するものと期待することができる。また、その重要性を誰もが認識しながらも乱流観測の空白域として残されてきたインドネシア多島海で、世界初となる乱流大規模観測を実施し、海面から海底直上までの乱流混合強度のプロファイルの取得に成功したことは、特筆すべき成果といえる。