Sack Lunch Seminar (SLS)

Rethinking carbon cycle feedbacks and the Urey weathering equation in the coupled carbon and sulfur system


The coupling of the carbon and sulfur cycles over the Cenozoic are often thought about in terms of the combined burial flux of pyrite and organic matter in marine sediments. However, the weathering of pyrite generates sulfuric acid that competes with CO2 as a source of protons to weather rocks on land. This coupling of the sulfur and carbon cycles via the input to the ocean can have dramatic effects on pCO2. We have been surveying the world’s rivers for their sulfur isotope variation in dissolved sulfate. The mean value is lower than previously assumed implying that pyrite oxidation and sulfuric acid weathering are more important than previously thought. In a restricted catchment in the Andes we have shown that this process leads to weathering as a source of CO2 not a sink. We show that this chemistry can be globalized into a new negative feedback in the ice-CO2 system.