A GLOBAL-MODEL FOR PRESENT-DAY ATMOSPHERIC SOIL CO2 CONSUMPTION BY CHEMICAL EROSION OF CONTINENTAL ROCKS (GEM-CO2)

The flux of atmospheric/soil CO2 consumed by chemical weathering of th e continents (F-CO2) can be estimated from river fluxes of bicarbonate s. Using published data for 232 small monolithologic watersheds, empir ical relationships between F-CO2 and runoff (Q) have been determined f or the major rock types outcropping on the continents. For validation, the models fitted to these relationships are applied to the Garonne, Congo and Amazon river basins to calculate the average CO2 consumption on these large river basins; the model results are close to previous estimates based on field measurements. The model (GEM-CO2: Global Eros ion Model for CO2 fluxes) is then applied at the global scale and allo ws the determination of latitudinal variations of the consumption of a tmospheric/soil CO2 by chemical erosion. The main results show that th e consumption of CO2 is mainly localized in the Northern hemisphere, b ecause of large continental area with a high proportion of carbonate r ocks, and in equatorial regions which are very humid. Finally, the mea n annual CO2 consumption for the whole continents amount to 0.26 Gt C y(-1), and 72% of this flux is removed in the Northern hemisphere.