Abstract:
AbstractPhysical weathering in cold, steep bedrock hillslopes occurs at rates that are thought to depend on temperature, but our ability to quantify the temperatureādependence of erosion remains limited when integrating over geomorphic timescales. Here, we present results from a 1D numerical model of ināsitu 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 nonāsteady state erosion, as well as the relationship between bedrock temperature, erosion rate, and erosional stochasticity. Our results suggest that even in stochastically eroding settings, 10Beāderived erosion rates of amalgamated samples can be used to estimate longāterm 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 10Beāderived erosion rate and the longāterm 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 10Beā14Cā3He system in quartz offers a method to evaluate the temperatureāsensitivity of bedrock erosion rates in cold, highāalpine environments.
