CO2 condensation is a serious limit to the deglaciation of Earth-like planets

Martin Turbet; Francois Forget; Jeremy Leconte; Benjamin Charnay; Gabriel Tobie

doi:10.1016/j.epsl.2017.07.050

paper

CO2 condensation is a serious limit to the deglaciation of Earth-like planets

arXiv:1703.04624 · doi:10.1016/j.epsl.2017.07.050

Abstract

It is widely believed that the carbonate-silicate cycle is the main agent to trigger deglaciations by CO $_{2}$ greenhouse warming on Earth and on Earth-like planets when they get in frozen state. Here we use a 3D Global Climate Model to simulate the ability of frozen planets to escape from glaciation by accumulating enough gaseous CO $_{2}$ . We find that Earth-like planets orbiting a Sun-like star may never be able to escape from glaciation if their orbital distance is greater than $\sim$ 1.27 AU (Flux $<$ 847 W m $^{- 2}$ or 62 $%$ of the Solar constant), because CO $_{2}$ would condense at the poles forming permanent CO $_{2}$ ice caps. This limits the amount of CO $_{2}$ in the atmosphere and thus its greenhouse effect. The amount of CO $_{2}$ that can be trapped in the polar caps depends on the efficiency of CO $_{2}$ ice to flow laterally as well as its graviational stability relative to subsurface water ice. The flow of CO $_{2}$ ice from poles to equator is mostly controlled by the bottom temperature, and hence by the internal heat flux. We find that a frozen Earth-like planet located at 1.30 AU of a Sun-like star could store as much as 1.5/4.5/15 bars of dry ice at the poles, for internal heat fluxes of 100/30/10 mW m $^{- 2}$ . But these amounts are lower limits. For planets with a significant water ice cover, we show that CO $_{2}$ ice deposits should be gravitationnally unstable. They get buried beneath the water ice cover in geologically short timescales of $\sim$ ~10 $^{4}$ yrs, mainly controlled by the viscosity of water ice. CO $_{2}$ would be permanently sequestered underneath the water ice cover, in the form of CO $_{2}$ liquids, CO $_{2}$ clathrate hydrates and/or dissolved in subglacial water reservoirs (if any). This would considerably increase the amount of CO $_{2}$ trapped and further reduce the probability of deglaciation.

45 pages, 7 figures, accepted for publication in EPSL

CO2 condensation is a serious limit to the deglaciation of Earth-like planets

Abstract

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