Impact of deglacial melt of the Cordillera Ice Sheet on the Gulf of Alaska coastal environment: geochemical and molecular biological analyses of marine sediments

• Project/Area Number: 17H01853
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Environmental dynamic analysis
• Research Institution: University of Toyama
• Principal Investigator: Keiji Horikawa 富山大学, 学術研究部理学系, 准教授 (40467858)
• Co-Investigator(Kenkyū-buntansha): 酒徳 昭宏 富山大学, 学術研究部理学系, 講師 (20713142) ; 酒井 英男 富山大学, 大学院理工学研究部(理学), 名誉教授 (30134993) ; 関 宰 北海道大学, 低温科学研究所, 准教授 (30374648) ; 村山 雅史 高知大学, 教育研究部総合科学系複合領域科学部門, 教授 (50261350)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥18,330,000 (Direct Cost: ¥14,100,000、Indirect Cost: ¥4,230,000); Fiscal Year 2019: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000); Fiscal Year 2018: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2017: ¥10,920,000 (Direct Cost: ¥8,400,000、Indirect Cost: ¥2,520,000)
• Keywords: アラスカ湾 / 融氷期 / コルディレラ氷床 / 生物生産 / 環境DNA / 山岳氷河融解 / 環境変動 / 地球化学 / アラスカ

Outline of Final Research Achievements

We collected a piston core sediment of ~8.5 m long at ~700 m water depth from the Gulf of Alaska. The 14C measurements of planktonic foraminifera represented the sediments record the past ~17 kyr ago. We obtained non-destructive XRF core scanner element data, Sr-Nd-Pb isotopes of bulk sediments, planktonic foraminifera d13C and d18O, biomarker data, and IRD data semi-quantitatively estimated by image analysis, and we found that C37:4 alkenone data clearly highlight an enormous meltwater peak at the YD that was not yet well known previously. We plan to publish this data in coming June 2020, and the other data set obtained by this reserach will be published later.

Academic Significance and Societal Importance of the Research Achievements

約2万年前の氷期には，北アメリカ北西部に現在のグリーンランド氷床に匹敵する量の氷床が存在していた（コルディレラ氷床）．先行研究では，14.5-14.0万年前の全球の温暖化とともにコルディレラ氷床の半分が一気に融解したと考えられてきたが，本研究では，大規模な融解は14万年頃と12万前頃の２度に分けて発生していたことを新たに明らかにした．融解史が明らかになったことで，氷床モデルの高精度化に貢献する．

Research Products

• [Journal Article] Millennial-scale fluctuations in water volume transported by the Tsushima Warm Current in the Japan Sea during the Holocene (2019)
  • Author(s): Horikawa, K., T. Kodaira, K. Ikehara, M. Murayama, and J. Zhang
  • Journal Title: Global and Planetary Change Volume: - Pages: 103028-103028
  • DOI: 10.1016/j.gloplacha.2019.103028
  • Peer Reviewed
• [Presentation] The advantages and limits of ITRAX core scanner: Learning by comparison with destructive element and isotope data from the Gulf of Alaska sediment core (2020)
  • Author(s): Keiji Horikawa, Nurunnabi MD Mondal, Masafumi MURAYAMA, Katsuya Nejigaki, Osamu Seki, Yusuke Okazaki
  • Organizer: JPGU 2020
  • Invited
• [Presentation] Deglacial productivity changes reflect XRF Br fueled by Cordilleran Ice Sheet dynamics (2020)
  • Author(s): Md Nurunnabi Mondal, Keiji Horikawa, Katsuya Nejigaki, Hideki Minami, Masafumi MURAYAMA, Osamu Seki, Yusuke Okazaki
  • Organizer: JPGU 2020
• [Presentation] Response of biological production in iron-enrich coastal Gulf of Alaska from glacier melting at past meltwater events (2019)
  • Author(s): Mondal MD Nurunnabi, 堀川恵司他
  • Organizer: 東京大学大気海洋研究所共同利用研究集会 GEOTRACES-Japanの現状と今後の展開
• [Presentation] 白鳳丸KH17-3次航海におけるアラスカ湾でのコア試料採泥と今後の展開 (2017)
  • Author(s): 堀川恵司，村山雅史，関宰
  • Organizer: 日本第四紀学会
• [Presentation] 1973-74年(ラニーニャ年)と2014-15年（エルニーニョ年）の西赤道太平洋表層海水に見られる酸素同位体比の大きな変化 (2017)
  • Author(s): 堀川恵司，西田絵里奈，小平智弘，張勁
  • Organizer: 日本地球化学会