Atmospheric oxygenation as a potential trigger for climate cooling

Abstract

Secular changes in atmospheric CO₂ and consequent global climate variations, are commonly attributed to global outgassing and the efficiency of silicate weathering, which may have been linked to mountain formation, land/arc distribution, and plant colonization through geological time. Although oxidative weathering has been shown to exert a significant role in the propagation of weathering fronts through the oxidation of Fe-bearing minerals, the influence of atmospheric O₂ concentration (pO₂) on silicate weathering, CO₂ consumption, and global climate has not been thoroughly evaluated. This study presents a numerical model aimed at estimating the effects of pO₂ on the climate, considering the influence of pO₂ on the regolith thickness and thus weathering duration of granitic domains. Our model simulations reveal that an increase in weathering efficiency, through deeper penetration of the oxidative weathering front in the granitic regolith, would independently introduce a steady-state climate cooling of up to ∼8 °C, in step with one-order of magnitude rise in pO₂. This temperature change may have repeatedly initiated the runaway ice-albedo feedback, leading to global glacial events (e.g., Neoproterozoic Snowball Earth). Increasing granitic weathering efficiency caused by a substantial pO₂ increase may also have contributed to the development of icehouse climate during the Phanerozoic.