A mechanism to explain the timing of glaciations related to orogenic episodes

Over very long timescales, mountain building or orogenesis is associated with increased weathering, the drawdown of atmospheric CO₂, and global cooling. Considering the Phanerozoic glaciation in particular, a multimillion‐year delay appears to exist between peaks in low‐latitude mountain uplift and the maximum extent of glaciation, implying a complex causal relationship between them. We show, using a combination of physical climate/circulation modelling and geochemical modelling approaches, that global silicate weathering can be modulated by orogeny in three distinct phases. High, young mountain ranges experience preferential precipitation and the highest erosion. As mountain ranges denude, precipitation decreases, but runoff temperature rises, sharply increasing chemical weathering potential and CO₂ drawdown. In the final phase, erosion and weathering are throttled by flatter topography. We hypothesise that orogeny acts as a capacitor in the climate system, granting the potential for intense transient CO₂ drawdown when mountain ranges are denuded. Intriguingly, depending on the future evolution of the Tibetan Plateau, the mechanism suggests such a scenario potentially happening 10–50 × 10⁶ years in the future.