Driven by a chemical non-equilibrium between parent material and water transporting dissolved CO2, the rates of chemical weathering in the regolith depend on both geological and hydro-climatic factors. The former supply fresh minerals, whereas the latter impact the production and transport of CO2 as well as the water transit time in the weathering zone, which determines the time available to the reaction to reach equilibrium. Although some mechanisms controlling or limiting weathering rates over large temporal and spatial scales have been identified, e.g., with respect to the supply rate of minerals and the water transit time, considerable debate still centers on the factors that in concert affect chemical weathering and their relative importance. Here we present a theoretical framework that relates all the important hydro-climatic and geologic quantities to chemical weathering. Applying the Π-theorem, the key dimensionless groups governing the weathering rates are obtained, providing insights into the joint effects of different factors affecting weathering and allowing us to directly compare measurements from sites with different climatic and geologic conditions. Based on the values assumed by all dimensionless quantities, we categorize the different limiting regimes and provide analytical expressions for the corresponding weathering rates. A hitherto unrecognized limiting regime, determined by low supply of CO2 is also identified. Existing measurements of weathering rates across the globe are reinterpreted and discussed in light of these results.
Calabrese, Salvatore, and Amilcare Porporato (2019): The Dimensionless Groups of Chemical Weathering: Disentangling the Role of Hydroclimatic and Geological Factors. American Geophysical Union Fall Meeting, San Francisco, CA, December 9-13, 2019.
This Paper/Book acknowledges NSF CZO grant support.