Persistent silicate weathering and carbon dioxide uptake in eolian drylands since the late Pliocene

Semi-arid and arid regions are largely omitted from long-term geological-scale carbon budgets due to the assumed weakness of silicate weathering. Here we reconstruct annual carbon dioxide (CO₂) consumption by silicate weathering (CO₂(SIW)) using red clay and loess–paleosol sequences from the Chinese Loess Plateau (CLP). We show that variability in eolian mass accumulation rate, rather than intrinsic silicate weathering intensity, primarily controls CO₂(SIW), consistent with persistently low-to-moderate chemical weathering across the CLP. Scaling these results to global eolian-deposited regions reveals that CO₂(SIW) increased from ~3.7 to ~18.8 Tg C yr⁻¹ between 4.0 and 1.0 Ma, followed by a decline to ~13.0 Tg C yr⁻¹ thereafter. This long-term trend broadly coincides with the late Pliocene decrease in atmospheric CO₂. Our findings provide a quantitative, million-year-scale budget of dryland CO₂ drawdown by silicate weathering and highlight eolian-dominated drylands systems as a previously underrecognized component of positive feedbacks in the global carbon cycle. “Red clay and loess-paleosol records from the Chinese Loess Plateau reveal that mass accumulation rate variability drives silicate-weathering CO₂ consumption in arid and semi-arid regions, closely tracking the late Pliocene atmospheric CO₂ decline.”