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 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. 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 1.27 AU (Flux 847 W m or 62 of the Solar constant), because CO would condense at the poles forming permanent CO ice caps. This limits the amount of CO in the atmosphere and thus its greenhouse effect. The amount of CO that can be trapped in the polar caps depends on the efficiency of CO ice to flow laterally as well as its graviational stability relative to subsurface water ice. The flow of CO 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. But these amounts are lower limits. For planets with a significant water ice cover, we show that CO ice deposits should be gravitationnally unstable. They get buried beneath the water ice cover in geologically short timescales of ~10 yrs, mainly controlled by the viscosity of water ice. CO would be permanently sequestered underneath the water ice cover, in the form of CO liquids, CO clathrate hydrates and/or dissolved in subglacial water reservoirs (if any). This would considerably increase the amount of CO trapped and further reduce the probability of deglaciation.
45 pages, 7 figures, accepted for publication in EPSL