Investigation of 3D structure of deep circulation driven by the geothermal heat and its influence on ocean material cycles

• Project/Area Number: 15K17765
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Japan, Meteorological Research Institute
• Principal Investigator: Urakawa Shogo 気象庁気象研究所, 海洋・地球化学研究部, 主任研究官 (00733916)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000); Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2017: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2016: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2015: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: 海底熱源 / 熱塩循環 / 深層循環 / 物質循環 / 海洋大循環モデル / 子午面循環

Outline of Final Research Achievements

Influences of the geothermal heat on the ocean deep circulation and material cycles were quantitatively investigated with the use of an ocean general circulation model. The geothermal heat enhanced the Pacific deep circulation by 17%, which led to improvements in dissolved oxygen and CFC-11 concentration in the bottom of the Pacific ocean. It also resulted in the improved representation of hypoxic water in the Eastern Tropical Pacific. On the other hand, it is found that the geothermal heat had only a limited effect on the net primary production in the ocean.

Academic Significance and Societal Importance of the Research Achievements

太平洋深層循環は毎秒1千万トンもの水の移動を伴う巨大な循環である。多量の水の移動は多くの物質の輸送を伴い、炭素循環などの海洋物質循環にも影響する。太平洋深層循環は海底熱源によって強化されることが先行研究からわかっているが、この循環の変化が物質循環に与える影響はこれまでほとんど研究されてこなかった。気候形成に強く関連する炭素循環に対しての影響は限定的だが、溶存酸素やフロン類などの複数の化学物質に対して大きな影響を持つことがわかった。本研究は海底熱源の重要性を様々な海洋物質循環の観点から明らかにし、海洋物質循環シミュレーションの高精度化に資する情報を創出しており、その学術的・社会的意義は高い。

Research Products

• [Presentation] Influence of enhanced deep circulation due to geothermal heat on biogeochemical cycle in the Pacific Ocean (2019)
  • Author(s): Shogo Urakawa, Hideyuki Nakano, Hiroyuki Tsujino, Kei Sakamoto, Takahiro Toyoda, Goro Yamanaka
  • Organizer: Japan Geoscience Union Meeting 2019
  • Int'l Joint Research
• [Presentation] Reproducibility of BMOC in a global ocean model: sensitivity on isopycnal diffusion scheme (2018)
  • Author(s): Urakawa, L. S., H. Tsujino, H. Nakano, K. Sakamoto, G. Yamanaka, and T. Toyoda
  • Organizer: 2018 Ocean Sciences Meeting
  • Int'l Joint Research
• [Presentation] Global ocean model development for CMIP6 in Meteorological Research Institute and its performance in reproducing ocean general circulation (2017)
  • Author(s): Urakawa, L. S., H. Tsujino, H. Nakano, K. Sakamoto, and G. Yamanaka
  • Organizer: JpGU-AGU Joint Meeting 2017
  • Int'l Joint Research
• [Presentation] 気候値外力実験における気象研全球海洋モデルGONDOLA_100の深層循環再現性評価 (2017)
  • Author(s): 浦川昇吾, 辻野博之, 中野英之, 坂本圭, 豊田隆寛, 山中吾郎, S. Yeager, W. Kim, G. Danabasoglu
  • Organizer: 日本海洋学会2017年度秋季大会
• [Presentation] 深層循環に対する海底熱源の影響についての再検証 (2016)
  • Author(s): 浦川昇吾, 辻野博之, 中野英之, 坂本圭, 山中吾郎
  • Organizer: 日本海洋学会2016年度秋季大会
  • Place of Presentation: 鹿児島大学郡元キャンパス