| Project/Area Number |
12640419
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Meteorology/Physical oceanography/Hydrology
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TAJIKA Eiichi Graduate School of Science, The University of Tokyo Research Associate, 大学院・理学系研究科, 助手 (70251410)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | glaciation / snowball Earth / Earth system / carbon cycle / Proterozoic |
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| Research Abstract |
Evidence for low-latitude glaciations during the Proterozoic suggests that the entire surface of the Earth may have been covered with ice and snow in these periods. In this study, I investigated such "snowball Earth Phenomena" with theoretical models.
The snowball Earth phenomena will be divided into four stages by dominant processes and their characteristic timescale. I found that there is a critical condition required for an initiation of the snowball Earth phenomena. At that condition, a net input flux of CO2 into the atmosphere-ocean system (=CO2 degassing rate due to volcanism + weathering rate of organic carbon - burial rate of organic carbon) becomes nearly zero. Therefore, the snowball Earth phenomena is occurred owing to imbalance of CO2 fluxes within the carbon cycle system.
The faint sun in the past may have been responsible for the repetition of snowball Earth phenomena during the Proterozoic. According to the analysis of the climate system and the carbon cycle system, however, an effect of lower luminosity of the sun should have been cancelled out completely by an effect of lower efficiency of chemical weathering rate due to lower soil biological activity during the Proterozoic. Therefore, the faint young sun may not have been the cause for the snowball Earth phenomena.
The carbon isotope mass balance model which uses variation of carbon isotope record of seawater during the Neoproterzoic suggests that organic carbon burial rate became very large just before the glaciations. This indicates increases in the consumption rate of atmospheric CO2, which may have initiated the snowball Earth phenomena during the Neoproterozoic.
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