Fig. 1.

Simplified long-term CO₂ feedbacks. Boxes show processes; ovals show hydrospheric constituents. Solid arrows show positive effect; dashed arrows show negative effect. (A) If terrestrial weathering is the only CO₂ regulator, the weathering flux must have the same steady state value regardless of weatherability. Increases in silicate weathering are nullified by pCO₂ falling. (B) Adding independent deep sea regulation allows for stable CO₂ under an altered silicate weathering flux, with stability maintained by a concurrent change in seafloor carbonatization rate. The balance dictates O₂ production, and may be shifted by enhancement of either process.