DOI: 10.1126/science.adk0957 ISSN: 0036-8075

CO 2 drawdown from weathering is maximized at moderate erosion rates

Aaron Bufe, Jeremy K. C. Rugenstein, Niels Hovius
  • Multidisciplinary

Uplift and erosion modulate the carbon cycle over geologic timescales by exposing minerals to chemical weathering. However, the erosion sensitivity of mineral weathering remains difficult to quantify. Solute-chemistry datasets from mountain streams in different orogens isolate the impact of erosion on silicate weathering—a carbon dioxide (CO 2 ) sink—and coupled sulfide and carbonate weathering—a CO 2 source. Contrasting erosion sensitivities of these reactions produce a CO 2 -drawdown maximum at erosion rates of ~0.07 millimeters per year. Thus, landscapes with moderate uplift rates bolster Earth’s inorganic CO 2 sink, whereas more rapid uplift decreases or even reverses CO 2 sequestration. This concept of an “erosion optimum” for CO 2 drawdown reconciles conflicting views on the impact of mountain building on the carbon cycle and permits estimates of geologic CO 2 fluxes dependent upon tectonic changes.

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