A Combined Cosmogenic Nuclides Approach for Determining the Temperature‐Dependence of Erosion
2022
Dennis, Donovan P. | Scherler, Dirk
Physical weathering in cold, steep bedrock hillslopes occurs at rates that are thought to depend on temperature, but our ability to quantify the temperature‐dependence of erosion remains limited when integrating over geomorphic timescales. Here, we present results from a 1D numerical model of in‐situ cosmogenic ¹⁰Be, ¹⁴C, and ³He concentrations that evolve as a function of erosion rate, erosion style, and ground surface temperature. We used the model to explore the suitability of these nuclides for quantifying erosion rates in areas undergoing non‐steady state erosion, as well as the relationship between bedrock temperature, erosion rate, and erosional stochasticity. Our results suggest that even in stochastically eroding settings, ¹⁰Be‐derived erosion rates of amalgamated samples can be used to estimate long‐term erosion rates, but infrequent large events can lead to bias. The ratio of ¹⁴C to ¹⁰Be can be used to evaluate erosional stochasticity, and to determine the offset between an apparent ¹⁰Be‐derived erosion rate and the long‐term rate. Finally, the concentration of ³He relative to that of ¹⁰Be, and the paleothermometric interpretations derived from it, are unaffected by erosional stochasticity. These findings, discussed in the context of bedrock hillslopes in mountainous regions, indicate that the ¹⁰Be‐¹⁴C‐³He system in quartz offers a method to evaluate the temperature‐sensitivity of bedrock erosion rates in cold, high‐alpine environments.
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