On the temporal variations of the atmospheric methane concentration by precise measurements of carbon and hydrogen isotopes.

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H03722
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Tohoku University
• Principal Investigator: MORIMOTO Shinji 東北大学, 理学研究科, 教授 (30270424)
• Co-Investigator(Kenkyū-buntansha): 青木 周司 東北大学, 理学研究科, 教授 (00183129) ; 後藤 大輔 国立極地研究所, 研究教育系, 助教 (10626386)
• Research Collaborator: ISHIJIMA kentaro
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: メタン / 温室効果気体 / 同位体比

Outline of Final Research Achievements

Systematic and precise measurements of the concentration and carbon and hydrogen isotope ratios of atmospheric methane were conducted by analyzing air samples regularly collected at northern high latitude sites, Antarctic station and in the western Pacific region, and their short-term, seasonal and long-term variations were identified. Simultaneous analysis with the concentration and isotope ratios suggested that the methane from microbial source could be responsible for the observed regrowth of the methane concentration after 2006 and after 2014. Simulations of the isotope ratios of the atmospheric methane with a three-dimensional atmospheric chemistry-transport model and prescribed methane inventory data gave isotopically lighter results than the observed values in this study. This indicates that the contribution ratio of each source category in the prescribed inventory is different from the real methane sources.

Free Research Field

大気科学

Academic Significance and Societal Importance of the Research Achievements

大気中メタン濃度観測のみからはメタン放出源に関する情報が得られないが、その炭素・水素同位体比の同時高精度観測を行うことにより、メタン放出源の変動に関する情報が得られることが示された。現在の地球表層におけるメタン循環を明らかにし、将来のメタン濃度予測精度を高めるために、メタン濃度と同位体比の同時観測が非常に有効である。