[B-PT05] 地球史解読：冥王代から現代まで

[BPT05-P09] 太古代における地球表層環境と海洋生物活動への制約

*中川 裕介¹、洪 鵬²、尾崎 和海³、田近 英一¹ (1.東京大学大学院新領域創成科学研究科、2.東京大学総合研究博物館、3.東京大学大気海洋研究所)

キーワード：太古代、暗い太陽のパラドックス、嫌気性生物、メタンによる温室効果、鉛直1次元大気光化学－海洋生態系－生物地球化学循環モデル

In the Archean, the climate of the Earth may have been warmer than that of today in spite of the lower luminosity of the Sun at that period [1]. The greenhouse effect of methane, in addition to that of carbon dioxide, is considered to have maintained the warm climate [2, 3], however, previous studies do not support the methane flux required for the warm climate [4]. In this study, we developed a coupled model of 1-D atmospheric chemistry – ocean ecosystem – biogeochemical cycle in order to investigate the biogenic methane flux in the Archean. We found that the biogenic methane flux could have been high enough to maintain warm climate if we assume ecosystem composed of multiple anoxygenic phototrophs which uses hydrogen and iron, with acetogen and methanogens, because of the H₂–CH₂O–CH₄ and CO–CH₃COOH–CH₄ biogeochemical cycles driven by Fe-CH₂O-CH₄ biogeochemical cycle could amplify the methane production nonlinearly through the recycling processes of organic matters.
[1] Walker et al., 1982, Palaeogeography, Palaeoclimatology, Palaeoecology, 40, 1. [2] Pavlov et al., 2001, Journal of Geophysical Research: Planets, 106, 23267. [3] Haqq-Misra et al., 2008, Astrobiology, 8, 1127. [4] Kharecha et al., 2005, Geobiology, 3, 53.