惑星表層環境ー内部共進化変動モデルの研究開発

• Project/Area Number: 16K05547
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: 中川 貴司 国立研究開発法人海洋研究開発機構, 数理科学・先端技術研究分野, 主任研究員 (50396941)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Discontinued (Fiscal Year 2018)
• Budget Amount: ¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000); Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: 表層環境 / 海洋進化 / プレートテクトニクス / マントル対流 / 気候変動 / 炭素循環 / 水循環 / 地球システム進化 / マントルダイナミクス / マントル脱ガス

Outline of Annual Research Achievements

惑星内部変動モデルから見積もられる火山活動が起因する脱ガスによる温室効果ガスの供給量を用いて、惑星表層環境がどのように反応するか定量的に計算できるモデル開発を行った．惑星表層環境については、太陽からの放射エネルギーと惑星自体からの反射エネルギーのバランスで、表面温度の計算ならびに大気ー海洋中に存在する温室効果ガス（二酸化炭素）の量を計算し、気候状態の変動とプレートテクトニクスの相関関係を明らかにした．その結果、気候状態の変動は、スノーボールから高温環境を頻繁に行き来し、その変動の時間スケールは約3000万年程度であることが判明した．この時間スケールと脱ガス変動（火成活動）で規定されるマントル対流の特徴的時間スケールを比較すると、気候変動と脱ガスの時間スケールにある一致と見いだすことに成功した．つまり、長時間（数十億年）スケールでの、惑星全体における気候変動は、惑星深部のダイナミクスとなんらかの因果関係があることが推定することができる．
また、表層環境維持における海洋の存在が惑星表面のテクトニックな活動にどのような影響を受けるかを、マントル対流モデリングを用いて調べた結果、惑星全体に現在の地球海洋の10倍程度の水が存在することが、現在の地球表層の海洋の量を説明するためには、必要であろうと考えられる結果が得られた．しかし、この結果は、地球深部の水の飽和状態に依存するために、最大値の見積もりであると結論づけられる．しかし、沈み込みに伴って、地球深部（遷移層）に持ち込む水フラックスの実験的な見積もりとモデルによって計算された水フラックスを比べると、同程度のオーダーであり、得られた結果でも十分に地球海洋の進化史を説明できる可能性を示唆している．

Research Products

• [Journal Article] On the evolution of the water ocean in the plate-mantle system (2018)
  • Author(s): Nakagawa Takashi、Iwamori Hikaru、Yanagi Ryunosuke、Nakao Atsushi
  • Journal Title: Progress in Earth and Planetary Science Volume: 5 Issue: 1 Pages: 1-16
  • DOI: 10.1186/s40645-018-0209-2
  • Peer Reviewed / Open Access
• [Journal Article] On the numerical modeling of the deep mantle water cycle in global-scale mantle dynamics: The effects of the water solubility limit of lower mantle minerals (2017)
  • Author(s): Nakagawa Takashi
  • Journal Title: Journal of Earth Science Volume: 28 Issue: 4 Pages: 563-577
  • DOI: 10.1007/s12583-017-0755-3
  • Peer Reviewed
• [Journal Article] Long-Term Stability of Plate-Like Behavior Caused by Hydrous Mantle Convection and Water Absorption in the Deep Mantle (2017)
  • Author(s): Nakagawa Takashi; Iwamori Hikaru
  • Journal Title: Journal of Geophysical Research-Solid Earth Volume: 122 Issue: 10 Pages: 8431-8445
  • DOI: 10.1002/2017jb014052
  • Peer Reviewed
• [Journal Article] Global-scale water circulation in the Earth's mantle: Implications for the mantle water budget in the early Earth (2017)
  • Author(s): Nakagawa, T., and M. W. Spigelman
  • Journal Title: Earth and Planetary Science Letters Volume: 464 Pages: 188-199
  • DOI: 10.1016/j.epsl.2017.02.010
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Presentation] On the climate and magnetic evolution of Earth-like planets (2018)
  • Author(s): Takashi Nakagawa, Shintaro Kadoya, and Eiichi Tajika
  • Organizer: Japan Geoscience Union 2018 Meeting
• [Presentation] Climate evolution of the Earth-like planets with surface plate motion in a whole Earth system evolution model (2018)
  • Author(s): Takashi Nakagawa, Shintaro Kadoya, and Eiichi Tajika
  • Organizer: American Geophysical Union 2018 Fall Meeting
  • Int'l Joint Research
• [Presentation] Global-scale water-carbon cycle in mantle dynamics and its implication to climate evolution (2018)
  • Author(s): Takashi Nakagawa, Shintaro Kadoya, and Eiichi Tajika
  • Organizer: International symposium on Study of Earth's deep interior
  • Int'l Joint Research
• [Presentation] Global-scale water-carbon cycle in mantle dynamics and its implication to climate evolution (2018)
  • Author(s): Takashi Nakagawa, Shintaro Kadoya, and Eiichi Tajika
  • Organizer: Gordon Research Conference on Deep Carbon Sciences
  • Int'l Joint Research
• [Presentation] Global-scale mantle dynamics: Core-mantle thermo-chemical coupling and volatile cycle (2017)
  • Author(s): Nakagawa Takashi; Iwamori Hikaru
  • Organizer: High Pressure Mineral Physics Seminar 9
  • Int'l Joint Research / Invited
• [Presentation] Numerical modeling on water cycle in plate-mantle dynamics system (2017)
  • Author(s): Nakagawa Takashi
  • Organizer: Chinese Geoscience Union
  • Int'l Joint Research / Invited
• [Presentation] On evolutionary climate tracks in deep mantle volatile cycle computed from numerical mantle convection simulations and its impact on the habitability of Earth-like planets (2017)
  • Author(s): Nakagawa Takashi; Tajika Eiichi; Kadoya Shintaro
  • Organizer: American Geophysical Union Fall Meeting
  • Int'l Joint Research
• [Presentation] 極限環境物質科学が固体地球システム進化に果たす役割 (2017)
  • Author(s): 中川貴司
  • Organizer: 第１回ポスト「京」萌芽的課題「基礎科学の挑戦」・「極限マテリアル」合同公開シンポジウム
  • Invited
• [Presentation] Insights from numerical modeling on the global-scale mantle water cycle: evolution of the surface water ocean as a constraint on the plate-mantle-core system (2016)
  • Author(s): Nakagawa, T., and M. W. Spiegelman
  • Organizer: American Geophysical Union 2016 Fall Meeting
  • Place of Presentation: San Francisco, USA
  • Year and Date: 2016-12-14
  • Int'l Joint Research
• [Presentation] Numerical modeling of global-scale water cycle in Earth's mantle and its influence to evolution of surface water ocean (2016)
  • Author(s): Nakagawa, T.
  • Organizer: 2016 Internation Conference on the Earth's Deep Interior
  • Place of Presentation: Wuhan, China
  • Year and Date: 2016-11-06
  • Int'l Joint Research
• [Presentation] On the mantle water cycle in global-scale plate-mantle dynamics system (2016)
  • Author(s): Nakagawa, T.
  • Organizer: 1st Asia-Pacific workshop on lithosphere and mantle dynamics
  • Place of Presentation: Taipei, Taiwan
  • Year and Date: 2016-09-23
  • Int'l Joint Research / Invited
• [Presentation] Effects on a stability of plate-like behavior in the global mantle water cycle (2016)
  • Author(s): Nakagawa, T., and M. W. Spiegelman
  • Organizer: 15th international symposium on Study of Earth's Deep Interior
  • Place of Presentation: Nantes, France
  • Year and Date: 2016-07-25
  • Int'l Joint Research
• [Presentation] Effects on a stability of plate-like behavior in the global mantle water cycle (2016)
  • Author(s): Nakagawa, T., and M. W. Spiegelman
  • Organizer: Workshop on the origin and evolution of plate tectonics
  • Place of Presentation: Ascona, Switzerland
  • Year and Date: 2016-07-18
  • Int'l Joint Research
• [Funded Workshop] 2nd Asia-Oceania Workshop on Lithosphere and Mantle Dynamics (2018)