Séminaire
Exports of terrestrial carbon (C) through the river network of the Amazon basin are non-negligible for its C budget, but have to date been ignored in future projections. I have recently developed ORCHILEAK, a new branch of ORCHIDEE, which simulates the cycling of dissolved organic C (DOC) and CO2 along the land-inland water continuum from the tree-tops to the coast and which has been tested and validated for the Amazon basin. I have used this model to simulate the coupled evolution of the terrestrial C balance and river C fluxes from 1860 to 2100. I show that the riverine C fluxes increase with rising atmospheric CO2 levels, with climate change only partly offsetting the CO2 fertilization effect on dissolved C production in soils. Land use change is of minor importance on these time scales. The C exports through the river network are higher than the land C sink over the entire simulation period, although they increase at a significantly lower rate. Cumulated over the period 1860-2100, the terrestrial C leakage through the river network in excess to the natural background fluxes equal 12% of the land C storage change but are more than twice as high as the increase in soil C stocks.