Discrimination method of suspended matter by ADCP and its application to investigation of material circulation

• Project/Area Number: 20K20933
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 17:Earth and planetary science and related fields
• Research Institution: Hokkaido University
• Principal Investigator: OHSHIMA Keiichiro 北海道大学, 低温科学研究所, 教授 (30185251)
• Co-Investigator(Kenkyū-buntansha): 深町 康 北海道大学, 北極域研究センター, 教授 (20250508) ; 伊藤 優人 国立極地研究所, 先端研究推進系, 特任研究員 (40887907)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥6,370,000 (Direct Cost: ¥4,900,000、Indirect Cost: ¥1,470,000); Fiscal Year 2021: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000); Fiscal Year 2020: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
• Keywords: ADCP / 体積後方散乱 / 物質循環 / 海中浮遊物 / フラジルアイス / 動物プランクトン / 巻き上がり / CEOF解析 / 海氷

Outline of Research at the Start

超音波のドップラーシフトを用いて流速を計るADCPからは、後方散乱強度データも得られるが、今までほとんど使われることはなかった。本研究は、ADCPの散乱強度データから、海中浮遊物のシグナルを取り出し、それが何なのか(①生物活動、②堆積物の巻き上がり、③海中内部の海氷)を識別する手法を開発することをめざす。最近の研究から、海洋の生物生産量を決める主要因となる鉄は、海底堆積物の巻き上がりにより供給されることが示唆されている。本手法開発が成功すると、多数の未使用のADCP散乱強度データから、堆積物巻き上がりとその生物活動との関係がわかり、物質循環研究に大きな貢献をもたらし得る。

Outline of Final Research Achievements

ADCP (Acoustic Doppler Current Profiler) is an instrument that measures the velocity profile using the Doppler Shift of reflected waves from scatterers in the ocean. We have developed the discrimination method of suspended matter from the ADCP volume backscatter data, which have not been used generally. Specifically, we discriminate among zooplankton, resuspended sediment, and frazil ice, using Complex EOF (CEOF) and bandpass filtering. Application of the method clarified the deep-penetrating frazil ice down to nearly 100m and diurnal vertical migration of zooplankton controlled by moonlight, which helps investigation of material circulation and biological productivity.

Academic Significance and Societal Importance of the Research Achievements

ADCPの散乱強度は、動物プランクトンの活動や、生物生産に不可欠な鉄を含む海底堆積物の巻き上がりといった、物質循環や生物生産にとって非常に重要な現象を捉えている可能性がある。しかし、何千何万にも及ぶADCPの散乱強度データが世界中において眠ったままになっている。本課題の手法は、これらのデータを活かすことに繋がる研究であり、発展させることで堆積物の巻き上がりのグローバルマッピングなども実現しうるものである。本研究で明らかになった海中深くのフラジルアイス形成は深層大循環を駆動する南極底層水の起源水生成機構を示す研究と言える。

Research Products

• [Int'l Joint Research] ワシントン大学/アラスカ大学(米国)
• [Int'l Joint Research] ワシントン大学/アラスカ大学(米国)
• [Int'l Joint Research] ワシントン大学/アラスカ大学(米国)
• [Journal Article] Particle-tracking experiments of coastal-origin sea ice that could induce high biological productivity in the Sea of Okhotsk (2022)
  • Author(s): Kuga Mizuki、Ohshima Kay I.、Kimura Noriaki、Nakata Kazuki、Fukamachi Yasushi
  • Journal Title: Journal of Oceanography Volume: 79 Issue: 2 Pages: 145-159
  • DOI: 10.1007/s10872-022-00670-5
  • Peer Reviewed
• [Journal Article] Dominant frazil ice production in the Cape Darnley polynya leading to Antarctic Bottom Water formation (2022)
  • Author(s): Ohshima, K. I., Y. Fukamachi, M. Ito, K. Nakata, D. Simizu, K. Ono, D. Nomura, G. Hashida, T. Tamura
  • Journal Title: Science Advances Volume: 8 Issue: 42
  • DOI: 10.1126/sciadv.adc9174
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Mapping of Active Frazil and Sea Ice Production in the Northern Hemisphere, With Comparison to the Southern Hemisphere (2022)
  • Author(s): Nakata K., K. I. Ohshima
  • Journal Title: Journal of Geophysical Research: Oceans Volume: 127 Issue: 12
  • DOI: 10.1029/2022jc018553
  • Peer Reviewed / Open Access
• [Journal Article] Improved SSM/I Thin Ice Algorithm with Ice Type Discrimination in Coastal Polynyas (2021)
  • Author(s): Kashiwase, H., K. I. Ohshima, K. Nakata, and T. Tamura
  • Journal Title: Journal of Atmospheric and Oceanic Technology Volume: 38 Issue: 4 Pages: 823-835
  • DOI: 10.1175/jtech-d-20-0145.1
  • Peer Reviewed / Open Access
• [Journal Article] Underwater frazil ice and its suspension depth detected from ADCP backscatter data around sea ice edge in the Sea of Okhotsk (2021)
  • Author(s): Ito Masato、Ohshima Kay I.、Fukamachi Yasushi、Mizuta Genta、Kusumoto Yoshimu、Kikuchi Takashi
  • Journal Title: Cold Regions Science and Technology Volume: 192 Pages: 103382-103382
  • DOI: 10.1016/j.coldregions.2021.103382
  • Peer Reviewed
• [Journal Article] The Prominent Spring Bloom and Its Relation to Sea‐Ice Melt in the Sea of Okhotsk, Revealed by Profiling Floats (2021)
  • Author(s): Kishi S., Ohshima K. I., Nishioka J., Isshiki N., Nihashi S., Riser S. C.
  • Journal Title: Geophysical Research Letters Volume: 48 Issue: 6
  • DOI: 10.1029/2020gl091394
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Mapping of Active Frazil for Antarctic Coastal Polynyas, With an Estimation of Sea‐Ice Production (2021)
  • Author(s): Nakata K., Ohshima K. I., Nihashi S.
  • Journal Title: Geophysical Research Letters Volume: 48 Issue: 6
  • DOI: 10.1029/2020gl091353
  • Peer Reviewed / Open Access
• [Journal Article] Status and trends of Arctic Ocean environmental change and its impacts on marine biogeochemistry: Findings from the ArCS project (2021)
  • Author(s): Kikuchi Takashi、Nishino Shigeto、Fujiwara Amane、Onodera Jonaotaro、Yamamoto-Kawai Michiyo、Mizobata Kohei、Fukamachi Yasushi、Watanabe Eiji
  • Journal Title: Polar Science Volume: 27 Pages: 100639-100639
  • DOI: 10.1016/j.polar.2021.100639
  • Peer Reviewed / Open Access
• [Journal Article] Observational evidence of supercooling and frazil ice formation throughout the water column in a coastal polynya in the Sea of Okhotsk (2020)
  • Author(s): Ito M., Fukamachi Y., Ohshima K. I., Shirasawa K.
  • Journal Title: Continental Shelf Research Volume: 196 Pages: 104072-104072
  • DOI: 10.1016/j.csr.2020.104072
  • Peer Reviewed
• [Journal Article] Iron Supply by Subglacial Discharge Into a Fjord Near the Front of a Marine‐Terminating Glacier in Northwestern Greenland (2020)
  • Author(s): Kanna Naoya, Sugiyama Shin, Fukamachi Yasushi, Nomura Daiki, Nishioka Jun
  • Journal Title: Global Biogeochemical Cycles Volume: 34 Issue: 10
  • DOI: 10.1029/2020gb006567
  • Peer Reviewed / Open Access
• [Presentation] Dominating frazil-ice production in a coastal polynya leads to Antarctic Bottom Water formation (2022)
  • Author(s): Ohshima K. I., Fukamachi Y., Ito M., Nakata K., Simizu D., Ono K., Nomura D., Hashida G., Tamura T.
  • Organizer: AGU Ocean Sciences Meeting 2022
  • Int'l Joint Research
• [Presentation] Particle tracking experiments of the coastal-origin sea ice that could transport the sediments and induce high biological productivity in the Sea of Okhotsk (2022)
  • Author(s): Mizuki Kuga, Kay Ohshima, Noriaki Kimura, Kazuki Nakata, Yasushi Fukamachi
  • Organizer: AGU Ocean Sciences Meeting 2022
  • Int'l Joint Research
• [Presentation] Dominating frazil-ice production in a coastal polynya leads to Antarctic Bottom Water formation (2022)
  • Author(s): Ohshima, K. I., Y. Fukamachi, M. Ito, K. Nakata, D. Simizu, K. Ono, D. Nomura, G. Hashida, and T. Tamura
  • Organizer: AGU Ocean Science Meeting 2022, Online
  • Int'l Joint Research
• [Presentation] Particle tracking experiments of the coastal-origin sea ice that could transport the sediments and induce high biological productivity in the Sea of Okhotsk (2022)
  • Author(s): Kuga, M., K. I. Ohshima, N. Kimura, K. Nakata, and Y. Fukamachi
  • Organizer: AGU Ocean Science Meeting 2022, Online
  • Int'l Joint Research
• [Presentation] Mapping of active frazil for coastal polynyas in the Northern Hemisphere, with estimation of sea-ice production (2021)
  • Author(s): Nakata, K., and K. I. Ohshima
  • Organizer: JpGU Meeting 2021, Online
  • Int'l Joint Research
• [Presentation] Global mapping of sea-ice production and active-frazil area in coastal polynyas using a unified AMSR algorithm (2021)
  • Author(s): Nakata, K., and K. I. Ohshima
  • Organizer: AGU Fall Meeting 2021, Hybrid
  • Int'l Joint Research
• [Presentation] オホーツク海における沿岸起源海氷の行方：物質循環への役割 (2021)
  • Author(s): 久賀 みづき，大島 慶一郎，木村 詞明，中田 和輝，深町 康
  • Organizer: 2021年度日本海洋学会秋季大会、オンライン開催
• [Presentation] 統一薄氷厚アルゴリズムによる全球ポリニヤ・海氷生産量マッピング (2021)
  • Author(s): 中田 和輝，大島 慶一郎
  • Organizer: 2021年度日本海洋学会秋季大会、オンライン開催
• [Presentation] サハリン沖係留観測で得られたADCPデータを用いたフラジルアイスの存在深度の推定 (2021)
  • Author(s): 伊藤 優人，大島 慶一郎，深町 康，水田 元太，楠本 仁麦，菊地 隆
  • Organizer: 2021年度日本海洋学会秋季大会、オンライン開催
• [Presentation] Global mapping of sea-ice production and discovery of 4th Antarctic Bottom Water (2020)
  • Author(s): K. I. Ohshima, Y. Fukamachi, S. Nihashi, T. Tamura and K. Iwamoto
  • Organizer: Chozen International Symposium on Understanding the Transboundary Pollution along North-South Transect in western Pacific region
  • Int'l Joint Research / Invited
• [Presentation] Iron and nutrients supply to a fjord from glacier-induced pumping in northwestern Greenland (2020)
  • Author(s): Kanna, N., S. Sugiyama, Y. Fukamachi, D. Nomura and J. Nishioka
  • Organizer: The 11th Symposium on Polar Science, Online
  • Int'l Joint Research / Invited
• [Presentation] サハリン沖係留観測で得られたADCPデータを用いたフラジルアイスの存在深度の推定 (2020)
  • Author(s): 伊藤 優人, 大島 慶一郎, 深町 康, 水田 元太, 楠本 仁麦, 菊地 隆
  • Organizer: 日本海洋学会2020年度秋季大会，オンライン開催