Spontaneous generation and dissipation of near-inertial internal waves from the Kuroshio Front

• Project/Area Number: 24684036
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Tokyo University of Marine Science and Technology
• Principal Investigator: Nagai Takeyoshi 東京海洋大学, その他部局等, 助教 (90452044)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Project Status: Completed (Fiscal Year 2015)
• Budget Amount: ¥22,750,000 (Direct Cost: ¥17,500,000、Indirect Cost: ¥5,250,000); Fiscal Year 2015: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2014: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000); Fiscal Year 2013: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000); Fiscal Year 2012: ¥17,550,000 (Direct Cost: ¥13,500,000、Indirect Cost: ¥4,050,000)
• Keywords: 黒潮 / 近慣性内部波 / 乱流 / 微細構造 / フロント / 二重拡散対流 / 黒潮続流 / 自律型プロファイリングフロート / 蛇行 / 近慣性内部 / 熱塩フィラメント構造 / 渦 / 乱流混合 / 拡散 / 黒潮フロント / 乱流運動エネルギー散逸率 / 水温の微細構造 / サブダクション / 湧昇 / ソルトフィンガー / 海洋フロント / エネルギー散逸 / 中規模渦 / サブメソスケール

Outline of Final Research Achievements

In this study, a microstructure profiling float and EM-APEX floats were deployed along the Kuroshio Extension Front in July 2013. The observed velocity data by EM-APEX floats exhibits banded phase structures of near-inertial internal waves with pronounced thermohaline interleaving structures below 150 m depth along the Kuroshio Extension over 900 km. The measured microstructure data show that the turbulence within the thermohaline interleaving structures was relatively weaker but microscale thermal variance dissipation rates were very large. These results suggest that subinertial and near-inertial shear catalyze the formations of double-diffusion favorable conditions and promote vertical mixing of tracer under the Kuroshio Extension Front. The results from the numerical simulations suggest that these near-inertial waves with large amplitudes can be generated spontaneously from the Kuroshio with no external forcing.

Research Products

• [Int'l Joint Research] University of Massachusetts Dartmouth/Woods Hole Oceanographic Institution/NorthWest Research Associate(米国)
• [Journal Article] Evidence of enhanced double-diffusive convection below the main stream of the Kuroshio Extension (2015)
  • Author(s): Takeyoshi Nagai, Ryuichiro Inoue, Amit Tandon, Hidekatsu Yamazaki
  • Journal Title: Journal of Geophysical Research Volume: 120 Issue: 12 Pages: 8402-8421
  • DOI: 10.1002/2015jc011288
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Dominant role of eddies and filaments in the offshore transport of carbon and nutrients in the California Current System (2015)
  • Author(s): Takeyoshi Nagai, Nicolas Gruber, Hartmut Frenzel, Zouhair Lachkar, James C. McWilliams, Gian-Kasper Plattner
  • Journal Title: Journal of Geophysical Research Volume: 120 Issue: 8 Pages: 5318-5341
  • DOI: 10.1002/2015jc010889
  • Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Spontaneous Generation of Near-Inertial Waves by the Kuroshio Front (2015)
  • Author(s): Takeyoshi Nagai, Amit Tandon, Eric Kunze, Amala Mahadevan
  • Journal Title: Journal of Physical Oceanography Volume: 45 Issue: 9 Pages: 2381-2406
  • DOI: 10.1175/jpo-d-14-0086.1
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] 黒潮のマルチスケール栄養塩供給メカニズム (2015)
  • Author(s): 長井健容、相場美里、Sophie Clayton
  • Journal Title: 海洋と生物 Volume: 37 Pages: 469-477
  • Int'l Joint Research
• [Journal Article] 黒潮フロント域の栄養塩供給 (2015)
  • Author(s): 長井健容
  • Journal Title: 沿岸海洋研究 Volume: 53 Pages: 11-18
  • NAID: 130007797548
• [Journal Article] Fine scale phytoplankton community structure across the Kuroshio Front (2014)
  • Author(s): S. Clayton, T. Nagai, M.J. Follows
  • Journal Title: J. Plankton Res. Volume: 36 Issue: 4 Pages: 1017-1030
  • DOI: 10.1093/plankt/fbu020
  • Peer Reviewed
• [Journal Article] Mixing observations at a constricted channel of a semi-closed estuary: Tokyo Bay (2013)
  • Author(s): Y. Kokubu, H. Yamazaki, T. Nagai, E. Gross
  • Journal Title: Continental Shelf Research Volume: 69 Pages: 1-16
  • DOI: 10.1016/j.csr.2013.09.004
  • Peer Reviewed
• [Journal Article] Hypolimnetic turbulence generation associated with superposition of large-scale internal waves in a strongly stratified lake: Lake Biwa (2013)
  • Author(s): G. Auger, H. Yamazaki, T. Nagai, M. Kumagai C. Jiao
  • Journal Title: Limnology Volume: 13 Issue: 3 Pages: 229-238
  • DOI: 10.1007/s10201-013-0401-4
  • Peer Reviewed
• [Journal Article] Direct observations of microscale turbulence and thermohaline structure in the Kuroshio Front (2012)
  • Author(s): Takeyoshi Nagai, Amit Tandon.Hidekatsu Yamazaki, Mark J. Doubell, Scott Gallager
  • Journal Title: Journal of Geophysical Research, Oceans Volume: 117 Issue: C8 Pages: 7228-7248
  • DOI: 10.1029/2011jc007228
  • Peer Reviewed
• [Presentation] 黒潮続流直下で強化される二重拡散対流 (2016)
  • Author(s): 長井健容、井上龍一郎、Amit Tandon、山崎秀勝
  • Organizer: 日本海洋学会 春季大会
  • Place of Presentation: 東京大学安田講堂
  • Year and Date: 2016-03-15
• [Presentation] Evidence of enhanced double-diffusive convection below the main stream of the Kuroshio Extension (2016)
  • Author(s): Takeyoshi Nagai, Ryuichiro Inoue, Amit Tandon, Hidekatsu Yamazaki
  • Organizer: Ocean Sciences Meeting 2016
  • Place of Presentation: New Orleans
  • Year and Date: 2016-02-22
  • Int'l Joint Research
• [Presentation] Evidence of enhanced double-diffusive convection below the main stream of the Kuroshio Extension (2016)
  • Author(s): Takeyoshi Nagai, Ryuichiro Inoue, Amit Tandon, Hidekatsu Yamazaki
  • Organizer: Clivar Meeting
  • Place of Presentation: JAMSTEC横浜
  • Year and Date: 2016-01-12
  • Int'l Joint Research
• [Presentation] 黒潮フロントの栄養塩供給過程 (2015)
  • Author(s): 長井健容
  • Organizer: 日本海洋学会春季大会
  • Place of Presentation: 東京海洋大学
  • Year and Date: 2015-03-21
• [Presentation] 黒潮フロント域における栄養塩供給過程 (2014)
  • Author(s): 長井健容
  • Organizer: 日本海洋学会秋季大会
  • Place of Presentation: 長崎大学
  • Year and Date: 2014-09-17
• [Presentation] SEMI-LAGRANGIAN OBSERVATIONS OF NEAR-INERTIAL SHEAR AND TURBULENCE ALONG THE KUROSHIO FRONT (2014)
  • Author(s): Nagai, T., Inoue, R., Tandon, A., Kunze, E., Mahadevan, A.
  • Organizer: Ocean Sciences Meeting 2014 Honolulu
  • Place of Presentation: Honolulu Hawaii
• [Presentation] 黒潮流軸直下の乱流混合と近慣性シアの準ラグラン ジュ流観測 (2014)
  • Author(s): 長井健容, 井上龍一郎, A. Tandon, E. Kunze, A. Mahadevan, 長谷川大介, 山崎秀勝
  • Organizer: 日本海洋学会春季大会
  • Place of Presentation: 東京品川
• [Presentation] フロントにおける乱流混合 (2014)
  • Author(s): 長井健容
  • Organizer: 日本海洋学会春季大会 シンポジウム 渦と蛇行の解析手法の動向
  • Place of Presentation: 東京品川
  • Invited
• [Presentation] 乱流計フロート (2014)
  • Author(s): 長井健容
  • Organizer: 第1回アルゴユーザーミーティング
  • Place of Presentation: AMSTEC 東京事務所 共用会議室AB
  • Invited
• [Presentation] 黒潮躍層内の強い乱流混合と近慣性内部波 (2013)
  • Author(s): 長井健容, Tandon, Kunze, Mahadevan, 山崎秀勝
  • Organizer: 日本海洋学会春季大会
  • Place of Presentation: 東京海洋大学
  • Year and Date: 2013-03-23
• [Presentation] Near-inertial pathways from balanced flow to turbulent dissipation in the Kuroshio front (2012)
  • Author(s): Nagai, T., A. Tandon, E. Kunze, A. Mahadevan, H. Yamazaki and M.J. Doubell
  • Organizer: 2012 AGU Fall Meeting
  • Place of Presentation: San Francisco
  • Year and Date: 2012-12-06
• [Presentation] Turbulent dissipation, near-inertial waves generated in the Kuroshio Front (2012)
  • Author(s): Nagai, T., A. Tandon, H. Yamazaki, A. Mahadevan, E. Kunze, S.Gallager and M.J. Doubell
  • Organizer: MIT Hayashi Fund
  • Place of Presentation: Boston MIT(招待講演)
  • Year and Date: 2012-11-06
• [Remarks]
  • URL: http://www.takeyoshi.net/Research/index.html
• [Remarks] 黒潮フロントが励起する近慣性内部波に関するウェブサイト
  • URL: http://www2.kaiyodai.ac.jp/~tnagai/Research/kuroshioiw.html
• [Remarks] 蛇行から波へ
  • URL: http://www2.kaiyodai.ac.jp/~tnagai/Research/kuroshioiw.html
• [Remarks]
  • URL: http://www2.kaiyodai.ac.jp/~tnagai/LOCEANED/research/kuroshioturbo.html