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Climate and carbon cycle at geological timescale: mountain building, erosion and weathering.
Pierre Maffre
Jeudi 24/01/2019, 11h00-12h00
Bât. 714 P. 118, LSCE Orme des Merisiers

Climate may fluctuate at virtually all spatial and temporal scales. Over geological timescale (several million years),  global Earth climate is driven by the geological carbon cycle, which is defined by the exchange of carbon between “surface” reservoirs (atmosphere, oceans…) and rocks. A key point is the CO2 consumption by weathering of silicated rocks on continental surfaces,  which is at the core of Walker’s feedback stabilising Earth climate (Walker et al., JGR, 1981). Silicate weathering is affected by both climatic conditions and silicated rock abundance and weatherability (linked to erosion rates). Both aspect are influenced by the uplift of mountain ranges. Recent insights on the consequences of such an uplift —especially on atmosphere and ocean dynamics— have challenge the “classical” view of global Earth cooling by mountain building.
By means of numerical modelling of climate dynamics, silicate weathering and geological carbon cycle, we propose new perspectives on how and why climate may have changed with tectonics perturbation, and more generally erosion ones. A key point of this work has been the development of a numerical model for regolith, ie: the interface between deep Earth and surface envelops, where weathering reactions take place. This model has also been upgraded to simulate a potential tracer of weathering processes at geological timescale, which may help to validate or invalidate our findings. This tracer is lithium isotopes in marine sediments.

Contact : Sarah Amram
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