High sensitivity of the continental-weathering carbon dioxide sink to future climate change

According to future anthropogenic emission scenarios, the atmospheric CO2 concentration may double before the end of the twenty-first century(1). This increase is predicted to result in a global warming of more than 6 degrees C in the worst case(1). The global temperature increase will promote changes in the hydrologic cycle through redistributions of rainfall patterns and continental vegetation cover(1,2). All of these changes will impact the chemical weathering of continental rocks. Long considered an inert CO2 consumption flux at the century timescale, recent works have demonstrated its potential high sensitivity to the ongoing climate and land-use changes(3,4). Here we show that the CO2 consumption flux related to weathering processes increases by more than 50% for an atmospheric CO2 doubling for one of the most important Arctic watersheds: the Mackenzie River Basin. This result has been obtained using a process-based model of the chemical weathering of continental surfaces forced by models describing the atmospheric general circulation and the dynamic of the vegetation(5,6) under increased, atmospheric CO2. Our study stresses the potential role that weathering may play in the evolution of the global carbon cycle over the next centuries.