[B-PT23_30AM1] 地球史解読：冥王代から現代まで

[BPT23-01] Snowball Earth and GCM simulation

*丸山 茂徳¹、鈴木 遼平²、大淵 済³ (1.東京工業大学地球生命研究所、2.東京工業大学、3.独立行政法人海洋研究開発機構)

Numerical simulation of snowball Earth, using out-of-date supercomputer program has been performed recently in USA, France and Germany. It seems to be difficult to reconstruct Snowball state by their simulation, while freezing more than 55% of ocean. If continents are gathered along the equatorial region such as Rodinia in the case of Sturtian and Marinoan Snowball Earth in Neoproterozoic, total surface irradiance (TSI) seems plausible to be 95% of present day and CO2 level as same as today.However, if the atmospheric CO2 is 2-6 times more than today, Snowball state cannot appear (Voigt et al., 2011). More realistic CO2 concentration of Neoproterozoic Earth was 20-50 times more than today. In addition, the temperature fluctuation of Snowball Earth period, from Sturtian to Marinoan, was -40℃ to +40℃ and vice versa within a short period < 10 m.y. which seem to be impossible because input and output of CO2 by plate tectonics usually takes time more than several hundreds of millions years. GCM simulation exaggerates positive feedback of CO2 too much. It is time to remodel GCM, considering the amount of clouds and its effect.