The carbonate-silicate cycle and CO₂/climate feedbacks on tidally locked terrestrial planets

Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO₂ concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO₂ level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO₂ concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO₂ concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.