12:00 PM - 1:00 PM
Chemical rock weathering controls long term biogeochemical cycling. It is a source of nutrients and a sink of atmospheric CO2. To estimate global chemical weathering rates, we use empirical analyses of existing water quality data from a large number of catchments. Our results indicate that runoff, lithology and land cover are the main controls of chemical weathering fluxes at large scales. Other factors, which were identified in the laboratory or in local scale studies, do not leave significant signatures at large scale. In addition, our results highlight the importance of representing and resolving regional variability even at global scales. A small fraction of the global land area produces large proportions of the total global chemical weathering fluxes. Chemical weathering in these areas, but also other, less obvious, aspects of chemical weathering, like the influence of glaciers on biogeochemical matter fluxes, are ill constrained. They should receive more attention to enable a thorough understanding of the processes steering this major compartment of the earth system.