[M-IS15] 古気候・古海洋変動

[MIS15-04] 気候モデルを用いた白亜紀から現代までの放射強制力に対する風化フラックスの感度の変化に関する研究

*樋口 太郎¹、阿部 彩子¹、陳 永利¹ (1.東京大学大気海洋研究所)

キーワード：風化、気候モデル、水循環、白亜紀、始新世

Weathering is the action of altering or decomposing rocks and minerals on the earth's surface through contact with air and water. Also, substances produced by weathering are transported to the ocean via rivers, groundwater over a long time. Such a process is very important in considering the material circulation and climate change of the earth. For this reason, many previous studies have made an effort in order to elucidate variations in weathering over the history of the earth and relationship with climate changes (e.g., Otto-Bliesner, 1995). These studies indicate that changes in weathering fluxes were altered by changes in the temperature and hydrological circulation associated with changes in atmospheric CO₂ concentrations and geographic conditions throughout Earth's history. However, little is known about how weathering fluxes change with changes in CO₂ concentrations and orbital parameters in each period. In this study, we systematically investigated the responses of the weathering flux on the Cretaceous, Eocene, and modern geographical conditions to changes in atmospheric CO₂ concentration and the orbital parameters using an atmospheric-ocean-vegetation fully coupled model MIROC4m-LPJ (Hasumi and Emori, 2004) and several weathering indexes calculated by model-simulated runoff and surface temperature (e.g., Oliva et al., 2003). As a result, our simulations shows that the weathering flux more increases with increasing atmospheric CO₂ concentration in Cretaceous geographical condition compared to other conditions thorough the difference in the hydrological circulation changes.