CSDMS 2016 annual meeting poster KenFerrier
Transient responses of chemical erosion rates to perturbations in physical erosion rates in a simple model of regolith mineralogy
Abstract:
Regolith-mantled hillslopes respond to tectonic and climatic perturbations in a variety of ways over a variety of time scales. Here I explore the response of chemical erosion rates in regolith to transient perturbations in physical erosion rates using a simple numerical model for regolith mineralogy. In this 1-D column model, weathered regolith is eroded from the surface at a prescribed physical erosion rate E(t), which drives responses in the rate at which solutes are flushed from the regolith at a chemical erosion rate W(t). To explore the response of W to perturbations in E, I impose a Gaussian pulse in physical erosion rates and compute the time-varying response in W. This model predicts that changes in W lag changes in E by a time comparable to the regolith residence time. As a consequence of this lag, there is a hysteresis in the modeled response of W to perturbations in E, with different relationships between W and E over different periods of time during and after the pulse. This model also predicts that the resulting relationships between W and E should depend on the initial value of E relative to a maximum possible regolith production rate. That is, transient increases in E generate increases in W for some initial values of E, and generate decreases in W for other initial values of E. To the extent that this model reflects the behavior of chemical erosion rates in nature, these results imply that transient perturbations in physical erosion rates can complicate interpretation of the relationships between W and E inferred from fluvial solute and sediment flux measurements and from sediment cores.
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