Temperature control on CO 2 emissions from the weathering of sedimentary rocks

Sedimentary rocks can release carbon dioxide (CO 2 ) during the weathering of rock organic carbon and sulfide minerals. This sedimentary carbon could act as a feedback on Earth’s climate over millennial to geological timescales, yet the environmental controls on the CO 2 release from rocks are poorly constrained. Here, we directly measure CO 2 flux from weathering of sedimentary rocks over 2.5 years at the Draix-Bléone Critical Zone Observatory, France. Total CO 2 fluxes approached values reported for soil respiration, with radiocarbon analysis confirming the CO 2 source from rock organic carbon and carbonate. The measured CO 2 fluxes varied seasonally, with summer fluxes five times larger than winter fluxes, and were positively correlated with temperature. The CO 2 release from rock organic carbon oxidation increased by a factor of 2.2 when temperature increased by 10 °C. This temperature sensitivity is similar to that of degradation of recent-plant-derived organic matter in soils. Our flux measurements identify sedimentary-rock weathering as a positive feedback to warming, which may have operated throughout Earth’s history to force the surface carbon cycle.