Wetness controls on global chemical weathering

Abstract

The formation of soils, the evolution of the biosphere, and the CO2 content in the atmosphere are strongly impacted by chemical weathering. Due to its manifold importance for the long-term stability of the Critical Zone, it is crucial to link weathering rates to the environmental conditions affecting it and develop accurate rate laws for landscape evolution and carbon cycle modeling. Here we use the π theorem of dimensional analysis to provide a theoretical framework to global datasets of weathering rates. As a result, a strong relation between chemical depletion, precipitation and potential evapotranspiration synthesizes the primary role of wetness. Based on this finding, we estimate the spatial distribution of chemical depletion fraction and find that, globally, soils are 50% chemically depleted, 61% of the land is in kinetic-limited conditions, while only 1% is supply-limited. The remaining 38% of the land is in a transitional regime and susceptible to changes in wetness.