Modelled glacial and non-glacial HCO3-, Si and Ge fluxes since the LGM: little potential for impact on atmospheric CO2 concentrations and a potential proxy of continental chemical erosion, the marine Ge/Si ratio

The runoff and riverine fluxes of HCO3-, Si and Ge that arise from chemical erosion in non-glaciated terrain, are modelled at six time steps from the Last Glacial Maximum (LGM) to the present day. The fluxes that arise from the Great Ice Sheets are also modelled. Terrestrial HCO3- fluxes decrease during deglaciation, largely because of the reduction in the area of the continental shelves as sea level rises. The HCO3- fluxes. and the inferred consumption of atmospheric CO2 are used as inputs to a carbon cycle model that estimates their impact on atmospheric CO2 concentrations ((CO2)-C-atms). A maximum perturbation of (CO2)-C-atms by similar to 5.5 ppm is calculated, The impact of solutes from glaciated terrain is small in comparison to those from non-glaciated terrain. Little variation in terrestrial Si and Ge fluxes is calculated (< 10%). However, the global average riverine Ge/Si ratio may be significantly perturbed if the glacial Ge/Si ratio is high. At present. variations in terrestrial chemical erosion appear to have only a reduced impact on (CO2)-C-atms and only little influence on the global Si and Ge cycle and marine Ge/Si ratios during deglaciation. (C) 2002 Elsevier Science B.V. All rights reserved