Observational study on ice sheet-ocean interaction at Totten Ice Shelf, East Antarctica

• Project Area: Giant reservoirs of heat/water/material : Global environmental changes driven by the Southern Ocean and the Antarctic Ice Sheet
• Project/Area Number: 20H04961
• 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: National Institute of Polar Research (2021); Hokkaido University (2020)
• Principal Investigator: 平野 大輔 国立極地研究所, 南極観測センター, 助教 (30790977)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Project Status: Completed (Fiscal Year 2021)
• Budget Amount: ¥5,720,000 (Direct Cost: ¥4,400,000、Indirect Cost: ¥1,320,000); Fiscal Year 2021: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000); Fiscal Year 2020: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
• Keywords: 東南極 / トッテン氷河 / 暖水流入 / 氷床海洋相互作用 / 棚氷底面融解

Outline of Research at the Start

東南極で最も融解損失が加速しているトッテン棚氷のアイスフロントから大陸斜面における観測データの解析に基づき，トッテン棚氷の底面融解に寄与する沖合起源の暖水分布と循環場の特徴を把握する。アイスフロント域の係留時系列データの解析により，棚氷下への流入暖水特性の変動性を示すとともに，大陸棚東部のダルトンポリニヤでの海氷生産に伴う暖水変質との関連を明らかにする。最新の観測データを取り入れた数値モデル結果との相互比較を行い，現場観測ではカバーしきれない時空間スケールの氷床海洋相互作用の素過程も把握することで，トッテン棚氷域における氷床海洋相互作用の包括的な理解を目指す。

Outline of Annual Research Achievements

近年、南極氷床の質量損失が加速しており、全球海水準の上昇が懸念されている。氷床質量損失を加速させている主な要因は「周囲の海」による棚氷底面融解の促進であり、精度の高い海水準変動の将来予測には氷床質量損失に対する海洋の本質的な役割の理解が不可欠である。沖合暖水の流入による氷河の融解加速が相次いで報告されている西南極とは対照的に、東南極沿岸域は「冷たい海」として広く認識されてきた(Schmidtko et al., 2014)。
このような背景に対し、令和3年度以降の研究実績として、暖水流入に伴う東南極トッテン氷河域における顕著な融解プロセス（氷床・海洋相互作用）に関する以下の成果を得た。

（１）「開洋丸」により取得したトッテン氷河沖斜面域での観測データ（2019年2月）と衛星データから導出した海洋力学高度データを統合し、沖合暖水のコアは巨大定在渦の東側（南下流域）に分布してトッテン氷河方向へと効率的に輸送されている、という研究成果を国際誌に発表した（Hirano et al., 2021, Communications Earth & Environment）。

（２）「しらせ」によるトッテン大陸棚上での複数回の海洋・海底地形観測（59、61、63次隊）と数値モデルの結果を統合することで、上記の定在渦により流入した暖水が陸棚上のお椀状の深い地形に沿って時計回りに循環し、その一部が氷河前面の局所的な深いトラフ（幅10-20km、深さ>1000m）に誘われる形で最終的にトッテン棚氷下へと流入する、という沖合からトッテン氷河へと繋がる新たな暖水循環像を確立し、トッテン氷河域における顕著な氷床海洋相互作用の実態を明らかにした。この内容を国際誌に投稿し受理された（Hirano et al., Nature Communications, in press）。

Research Progress Status

令和3年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和3年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] University of Tasmania/CSIRO(オーストラリア)
• [Int'l Joint Research] The University of Texas/Scripps Institution of Oceanography(米国)
• [Journal Article] On-Shelf Circulation of Warm Water Toward the Totten Ice Shelf, East Antarctica (2023)
  • Author(s): Daisuke Hirano, Takeshi Tamura, Kazuya Kusahara, Masakazu Fujii, Kaihe Yamazaki, Yoshihiro Nakayama, Kazuya Ono, Takuya Itaki, Yuichi Aoyama, Daisuke Simizu, Kohei Mizobata, Kay I. Ohshima, Yoshifumi Nogi, Stephen R. Rintoul, Esmee van Wijk, Jamin S. Greenbaum, Donald D. Blankenship, Koji Saito, and Shigeru Aoki
  • Journal Title: Nature Communications Volume: in press
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Impacts of basal melting of the Totten Ice Shelf and biological productivity on marine biogeochemical components in Sabrina Coast, East Antarctica (2022)
  • Author(s): Tamura Tetsuya P.、Nomura Daiki、Hirano Daisuke、Tamura Takeshi、Kiuchi Masaaki、Hashida Gen、Makabe Ryosuke、Ono Kazuya、Ushio Shuki、Yamazaki Kaihe、Nakayama Yoshihiro、Takahashi Keigo D.、Sasaki Hiroko、Murase Hiroto、Aoki Shigeru
  • Journal Title: Global Biogeochemical Cycles Volume: in press Issue: 9
  • DOI: 10.1029/2022gb007510
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Warm surface waters increase Antarctic ice shelf melt and delay dense water formation (2022)
  • Author(s): Aoki Shigeru、Takahashi Tomoki、Yamazaki Kaihe、Hirano Daisuke、Ono Kazuya、Kusahara Kazuya、Tamura Takeshi、Williams Guy D.
  • Journal Title: Communications Earth & Environment Volume: 3 Issue: 1
  • DOI: 10.1038/s43247-022-00456-z
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Seasonal Variations and Drivers of Surface Ocean pCO2 in the Seasonal Ice Zone of the Eastern Indian Sector, Southern Ocean (2021)
  • Author(s): Tozawa Manami、Nomura Daiki、Nakaoka Shin‐ichiro、Kiuchi Masaaki、Yamazaki Kaihe、Hirano Daisuke、Aoki Shigeru、Sasaki Hiroko、Murase Hiroto
  • Journal Title: Journal of Geophysical Research: Oceans Volume: 127 Issue: 1
  • DOI: 10.1029/2021jc017953
  • Peer Reviewed / Open Access
• [Journal Article] Seasonal Evolution of Cape Darnley Bottom Water Revealed by Mooring Measurements (2021)
  • Author(s): Mizuta Genta、Fukamachi Yasushi、Simizu Daisuke、Matsumura Yoshimasa、Kitade Yujiro、Hirano Daisuke、Fujii Masakazu、Nogi Yoshifumi、Ohshima Kay I.
  • Journal Title: Frontiers in Marine Science Volume: 8
  • DOI: 10.3389/fmars.2021.657119
  • Peer Reviewed / Open Access
• [Journal Article] Shoreward intrusion of oceanic surface waters alters physical and biological ocean structures on the Antarctic continental shelf during winter: Observations from instrumented seals (2021)
  • Author(s): Kokubun Nobuo、Tanabe Yukiko、Hirano Daisuke、Mensah Vigan、Tamura Takeshi、Aoki Shigeru、Takahashi Akinori
  • Journal Title: Limnology and Oceanography Volume: 66 Issue: 10 Pages: 3740-3753
  • DOI: 10.1002/lno.11914
  • Peer Reviewed / Open Access
• [Journal Article] Poleward eddy-induced warm water transport across a shelf break off Totten Ice Shelf, East Antarctica (2021)
  • Author(s): Hirano Daisuke、Mizobata Kohei、Sasaki Hiroko、Murase Hiroto、Tamura Takeshi、Aoki Shigeru
  • Journal Title: Communications Earth & Environment Volume: 2 Issue: 1 Pages: 1-8
  • DOI: 10.1038/s43247-021-00217-4
  • Peer Reviewed / Open Access
• [Journal Article] Multidecadal poleward shift of the Southern Boundary of the Antarctic Circumpolar Current off East Antarctica (2021)
  • Author(s): Yamazaki, K., S. Aoki, K. Katsumata, D. Hirano, Y. Nakayama
  • Journal Title: Science Advances Volume: 7 Issue: 24
  • DOI: 10.1126/sciadv.abf8755
  • Peer Reviewed / Open Access
• [Journal Article] The effect of basal melting of the Shirase Glacier Tongue on the CO 2 system in L?tzow‐Holm Bay, East Antarctica (2021)
  • Author(s): Kiuchi Masaaki、Nomura Daiki、Hirano Daisuke、Tamura Takeshi、Hashida Gen、Ushio Shuki、Simizu Daisuke、Ono Kazuya、Aoki Shigeru
  • Journal Title: Journal of Geophysical Research: Biogeosciences Volume: － Issue: 5
  • DOI: 10.1029/2020jg005762
  • Peer Reviewed / Open Access
• [Journal Article] Modeling intensive ocean-cryosphere interactions in Luzow-Holm Bay, East Antarctica (2021)
  • Author(s): Kusahara Kazuya、Hirano Daisuke、Fujii Masakazu、Fraser Alexander D.、Tamura Takeshi
  • Journal Title: The Cryosphere Volume: 15 Issue: 4 Pages: 1697-1717
  • DOI: 10.5194/tc-15-1697-2021
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Reversal of freshening trend of Antarctic Bottom Water in the Australian-Antarctic Basin during 2010s (2020)
  • Author(s): Aoki S., Yamazaki K., Hirano D., Katsumata K., Shimada K., Kitade Y., Sasaki H., Murase H.
  • Journal Title: Scientific Reports Volume: 10 Issue: 1 Pages: 1-7
  • DOI: 10.1038/s41598-020-71290-6
  • Peer Reviewed / Open Access
• [Journal Article] Freshening of Antarctic Bottom Water Off Cape Darnley, East Antarctica (2020)
  • Author(s): Aoki S., Katsumata K., Hamaguchi M., Noda A., Kitade Y., Shimada K., Hirano D., Simizu D., Aoyama Y., Doi K., Nogi Y.
  • Journal Title: Journal of Geophysical Research: Oceans Volume: 125 Issue: 8 Pages: 1-13
  • DOI: 10.1029/2020jc016374
  • Peer Reviewed
• [Journal Article] Strong biological carbon uptake and carbonate chemistry associated with dense shelf water outflows in the Cape Darnley polynya, East Antarctica (2020)
  • Author(s): Murakami Kan, Nomura Daiki, Hashida Gen, Nakaoka Shin-ichiro, Kitade Yujiro, Hirano Daisuke, Hirawake Toru, Ohshima Kay I.
  • Journal Title: Marine Chemistry Volume: 225 Pages: 103842-103842
  • DOI: 10.1016/j.marchem.2020.103842
  • Peer Reviewed
• [Journal Article] Continuous winter oceanic profiling in the Cape Darnley Polynya, East Antarctica (2020)
  • Author(s): Aoki Shigeru, Ono Kazuya, Hirano Daisuke, Tamura Takeshi
  • Journal Title: Journal of Oceanography Volume: 76 Issue: 5 Pages: 365-372
  • DOI: 10.1007/s10872-020-00550-w
  • NAID: 40022348693
  • Peer Reviewed
• [Presentation] 東南極における氷床海洋相互作用の観測研究 (2022)
  • Author(s): 平野大輔
  • Organizer: 日本地質学会第129年学術大会
  • Invited
• [Presentation] 東南極トッテン棚氷周辺海域の海洋-海氷-棚氷数値モデリング (2022)
  • Author(s): 草原 和弥、平野 大輔、藤井 昌和、田村 岳史、溝端 浩平、青木 茂
  • Organizer: 日本海洋学会
• [Presentation] On-Shelf Circulation of Warm Water Toward the Totten Ice Shelf, East Antarctica (2022)
  • Author(s): Daisuke Hirano, Takeshi Tamura, Kazuya Kusahara, Masakazu Fujii, Kaihe Yamazaki, Yoshihiro Nakayama, Kazuya Ono, Takuya Itaki, Yuichi Aoyama, Daisuke Simizu, Kohei Mizobata, Kay I. Ohshima, Yoshifumi Nogi, Stephen R. Rintoul, Esmee van Wijk, Jamin S. Greenbaum, Donald D. Blankenship, Shigeru Aoki
  • Organizer: JpGU Meeting 2022
  • Int'l Joint Research
• [Presentation] On-shelf warm water circulation toward Totten Ice Shelf, East Antarctica (2021)
  • Author(s): Daisuke Hirano, Takeshi Tamura, Kazuya Kusahara, Masakazu Fujii, Kaihe Yamazaki, Yoshihiro Nakayama, Kazuya Ono, Takuya Itaki, Yuichi Aoyama, Daisuke Simizu, Kohei Mizobata, Kay I. Ohshima, Yoshifumi Nogi, Shigeru Aoki
  • Organizer: The 12nd Symposium on Polar research
• [Presentation] Difference of the pCO2 over two decades (1996 and 2019) in the eastern Indian sector of the Southern Ocean (2021)
  • Author(s): Manami Tozawa, Daiki Nomura, Shin-ichiro Nakaoka, Masaaki Kiuchi, Daisuke Hirano, Kaihe Yamazaki, Shigeru Aoki, Hiroko Sasaki, Hiroto Murase:
  • Organizer: The 12nd Symposium on Polar research
• [Presentation] Spatiotemporal high-resolution mapping of biological production in the Southern Ocean (2021)
  • Author(s): Xiangxing Lai, Xianliang Pan, Bofeng Li, Ryosuke Makabe, Daisuke Hirano, Yutaka Watanabe
  • Organizer: The 12nd Symposium on Polar research
• [Presentation] 東南極沖における南極周極流の南限の南下 (2021)
  • Author(s): 山崎 開平，青木 茂，勝又 勝郎，平野 大輔，中山 佳洋
  • Organizer: 日本海洋学会
• [Presentation] Seasonal and interannual variations of surface water carbonate chemistry in the Indian sector of the Southern Ocean (2021)
  • Author(s): Manami Tozawa, Daiki Nomura, Shin-ichiro Nakaoka, Masaaki Kiuchi, Daisuke Hirano, Shigeru Aoki, Hiroko Sasaki, Hiroto Murase
  • Organizer: JpGU Meeting 2021
  • Int'l Joint Research
• [Presentation] Summer carbonate chemistry near the Totten Ice Shelf, Sabrina Coast, East Antarctica (2021)
  • Author(s): Tetsuya Tamura, Daiki Nomura, Daisuke Hirano, Takeshi Tamura, Masaaki Kiuchi, Gen Hashida, Shigeru Aoki, Hiroko Sasaki, Hiroto Murase
  • Organizer: JpGU Meeting 2021
  • Int'l Joint Research
• [Presentation] Inflows of offshore-origin warm water toward Totten Ice Shelf region, East Antarctica (2020)
  • Author(s): Hirano, D., K. Mizobata, T. Tamura, M. Ito, K. Yamazaki, K. Yoichiro, M. Kiuchi, H. Murase, H. Sasaki, S. Aoki
  • Organizer: JpGU-AGU Joint Meeting 2020
  • Int'l Joint Research
• [Presentation] 係留系観測で得られたビンセネス湾沖南極底層水の時系列変化 (2020)
  • Author(s): 溝端 浩平, 北出 裕二郎, 嶋田 啓資, 平野 大輔, 松村 義正, 程 霊巧, 青木 茂, 田村 岳史
  • Organizer: JpGU-AGU Joint Meeting 2020
  • Int'l Joint Research
• [Presentation] Property of eddy and AABW observed off Cape Poinsett (2020)
  • Author(s): Kitade, Y., K. Mizobata, D. Hirano, K. Shimada, S. Aoki, and T. Tamura
  • Organizer: JpGU-AGU Joint Meeting 2020
  • Int'l Joint Research
• [Presentation] Poleward shift of the southern boundary of the Antarctic Circumpolar Current off East Antarctica (2020)
  • Author(s): Yamazaki, K.，S. Aoki，D. Hirano，K. Katsumata，Y. Nakayama
  • Organizer: JpGU-AGU Joint Meeting 2020
  • Int'l Joint Research
• [Presentation] Oceanographic and geophysical observation campaign off Sabrina Coast, East Antarctica, in 2019/2020 (2020)
  • Author(s): 青木 茂，田村 岳史，中山 佳洋，小野 数也，Wongpan Pat，山崎 開平，板木 拓也，徳田 悠希，佐々木 聡史，平野 大輔，青山 雄一
  • Organizer: JpGU-AGU Joint Meeting 2020
  • Int'l Joint Research
• [Presentation] 東南極トッテン棚氷の底面融解が海洋の炭酸系成分に与える影響 (2020)
  • Author(s): 田村 哲也, 野村 大樹, 平野 大輔, 田村 岳史, 木内 政彰, 橋田 元, 青木 茂, 佐々木 裕子, 村瀬 弘人
  • Organizer: 日本海洋学会2020年度秋季大会
• [Presentation] 南極海東インド洋セクターにおける海洋表面炭酸系成分の変化 (2020)
  • Author(s): 戸澤 愛美，野村 大樹，中岡 慎一郎，木内 政彰，平野 大輔，青木 茂, 佐々木 裕子，村瀬 弘人
  • Organizer: 日本海洋学会2020年度秋季大会
• [Presentation] The Heart of the East AnTarctic CRyosphere-Ocean Synergy System (HEAT-CROSS) (2020)
  • Author(s): Kohei Mizobata, Takeshi Tamura, Daisuke Hirano, and Ryosuke Makabe
  • Organizer: The 11th Symposium on Polar Science
• [Presentation] The effect of basal melting of the Totten Ice Shelf on marine biogeochemical components in Sabrina Coast, East Antarctica (2020)
  • Author(s): Tetsuya Tamura, Daiki Nomura, Daisuke Hirano, Takeshi Tamura, Masaaki Kiuchi, Gen Hashida, Shigeru Aoki, Hiroto Murase
  • Organizer: The 11th Symposium on Polar Science
• [Presentation] Variations of surface water carbonate chemistry from winter to summer in the Indian sector of the Southern Ocean (2020)
  • Author(s): Tozawa, M., D. Nomura, S. Nakaoka, M. Kiuchi, D. Hirano, S. Aoki, H. Muras
  • Organizer: The 11th Symposium on Polar Science