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Abstract Chemical erosion is of wide interest due to its influence on topography, nutrient supply to streams and soils, sediment composition, and Earth's climate. While controls on chemical erosion rate have been studied extensively in steady‐state models, few studies have explored the controls on chemical erosion rate during transient responses to external perturbations. Here we develop a numerical model for the coevolution of soil‐mantled topography, soil thickness, and soil mineralogy, and we use it to simulate responses to step changes in rates of rock uplift, soil production, soil transport, and mineral dissolution. These simulations suggest that tectonic and climatic perturbations can generate responses in soil chemical erosion rate that differ in speed, magnitude, and spatial pattern and that climatic and tectonic perturbations may impart distinct signatures on hillslope mass fluxes, soil chemistry, and sediment composition. The response time of chemical erosion rate is dominantly controlled by hillslope length and is secondarily modulated by rates of rock uplift, soil production, transport, and mineral dissolution. This strong dependence on drainage density implies that a landscape's chemical erosion response should depend on the relative efficiencies of river incision and soil transport and thus may be mediated by climatic and biological factors. The simulations further suggest that the timescale of the hillslope response may be long relative to that of river channel profiles, implying that chemical erosion response times may be limited more by the sluggishness of the hillslopes than by the rate of signal propagation through river channel profiles.
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Modeling Cosmogenic Nuclides in Transiently Evolving Topography and Chemically Weathering Soils
Abstract Terrestrial cosmogenic nuclides (TCN) are widely employed to infer denudation rates in mountainous landscapes. The calculation of an inferred denudation rate (Dinf) from TCN concentrations is typically performed under the assumptions that denudation rates were steady during TCN accumulation and that soil chemical weathering negligibly impacted soil mineral abundances. In many landscapes, however, denudation rates were not steady and soil composition was significantly impacted by chemical weathering, which complicates interpretation of TCN concentrations. We present a landscape evolution model that computes transient changes in topography, soil thickness, soil mineralogy, and soil TCN concentrations. We used this model to investigate TCN responses in transient landscapes by imposing idealized perturbations in tectonically (rock uplift rate) and climatically sensitive parameters (soil production efficiency, hillslope transport efficiency, and mineral dissolution rate) on initially steady‐state landscapes. These experiments revealed key insights about TCN responses in transient landscapes. (a) Accounting for soil chemical erosion is necessary to accurately calculateDinf. (b) Responses ofDinfto tectonic perturbations differ from those to climatic perturbations, suggesting that spatial and temporal patterns inDinfare signatures of perturbation type and magnitude. (c) If soil chemical erosion is accounted for, basin‐averagedDinfinferred from TCN in stream sediment closely tracks actual basin‐averaged denudation rate, showing thatDinfis a reasonable proxy for actual denudation rate, even in many transient landscapes. (d) Response times ofDinfto perturbations increase with hillslope length, implying that response times should be sensitive to the climatic, biological, and lithologic processes that control hillslope length.
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- Award ID(s):
- 2045433
- PAR ID:
- 10527583
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Earth Surface
- Volume:
- 128
- Issue:
- 10
- ISSN:
- 2169-9003
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1029/2023JF007201
