Understanding the interactions between tectonic processes, erosion, weathering and climate. New insights from the DynSoil-GEOCLIM modelling approach
Résumé
Earth's long-term climate stability is postulated to be maintained by the silicate weathering feedback. Long-term changes on Earth's surface can significantly affect the strength of this feedback and are proposed as drivers for climatic variations over the course of Earth History. Among these modulating processes, we focus on the role of erosion (eg, Milot et al. 2002, EPSL 196 83-98), regolith development and its shielding effect (eg, Godderis et al. 2014, Earth Sci Rev 128 122-138), and the exhumation of specific geological units, for instance mafic complexes during arc-continent collision (eg, Macdonald et al., 2019, Science 364 181-184). Understanding the interlinked effects of these processes throughout Earth History is a challenge for which numerical modeling can be helpful. The GEOCLIM model (Donnadieu et al., 2006, G3 7(11)) simulates geochemical cycles, specifically the carbon cycle, and climate dynamics on geological timescales. A newly implemented model for weathering fluxes (DynSoil) now explicitly simulates the interaction between physical erosion, climatology, and the development of chemical weathering profiles. We have integrated this model with global spatially resolved lithology to account for the varying carbon sequestration potential of different rock types. This model framework can be used to investigate the equilibrium state of carbon-climate system, as well as transient perturbations, accounting for the potential inertia of weathering profiles. Preliminary results have shown the ambiguous effect of mountain building that affects both climate circulation and continental erosion (Maffre et al. 2018, EPSL 493 174-185). Using this model, we show that the uplift of high weathering potential silicate rocks in the tropics can significantly drawdown atmospheric carbon dioxide and play a role in initiating glacial climate.