Mean bedrock-to-saprolite conversion and erosion rates during mountain growth and decline

Weathering and associated atmospheric CO2 consumption are thought to increase during the erosion of uplifting mountain ranges, but the effect of enhanced erosion on weathering is still the subject of active debate. We explore the possibility that erosion heterogeneity in uplifting landscapes significantly impacts the temporal relationships among mean uplift, erosion and weathering using a 3D landscape evolution model applied to a synthetic surface with different uplift and climate scenarios. Although we do not strictly simulate the weathering outflux of the mountain, we analyze the weathering response through the evolution of the mountain-mean saprolite production rate and compare it to the mountain-mean erosion rate through time. The parametrical analysis shows that the temporal relationship between the mean erosion and saprolite production rates depends mainly on the ratio of the maximum saprolite production rate and the uplift rate wm/U. We explore two end-members. (1) When wm/U>1, which corresponds to mountain ranges under a hot and humid climate, the mean erosion and saprolite production rates vary at the same rate during the uplift and after, once the uplift is stopped. When the uplift is stopped, the mean saprolite production increases and then decreases locally at different times. This heterogeneity induces an overall decrease in the mean saprolite production rate. (2) When wm/U