MODELING METEORIC 10-BERYLLIUM ACROSS VARYING LAND USE AND CLIMATIC HISTORIES: UNIQUE SCENARIOS AND SOURCE-SINK COUPLING

Nutrient and textural changes remain in soils up to a millennium after an environmental (climatic or anthropogenic) transition. Even subsistence agriculture can affect soils after hundreds of years, due to changes to the surface topography and water drainage systems. This research addresses the question: how well and how precisely does meteoric ¹⁰Beryllium, a quantity that varies with soil erosion, precipitation, dust deposition, and physical soil properties, record soil erosion and transport? To explore this, a simple numerical model of meteoric ¹⁰Be produces and samples synthetic data, and investigates uncertainties in interpreting forcings for both synthetic and measured data.

This model uses the known mechanics of meteoric ¹⁰Be accumulation in a 1-dimensional space and time grid to create virtual soil/bedrock columns which undergo prescribed (by user) erosion and deposition. Soil processes such as bioturbation affect the depth distribution of the proxy, and erosion and deposition dictate the inventory. This model works for both eroding and depositional environments, allowing for a dynamically-dimensioned soil column.

The second part of the module uses digital sampling to compare the apparent signal (analogous with measured concentrations from the field) with the initial forcing, and to answer such questions as: what are the ranges of environments and land uses that can form this profile? What sampling resolution is minimum to discern changes in erosion of varying magnitudes, timings, and durations?

Finally, the forward model combines eroded material to produce mixed downstream deposits. The user can define different hillslope transport laws, which determine the concentration of the deposited material: a) simple catchment average: concentrations equal to the average of the eroded material, b) spatial weighting of eroded material, c) temporal delays in the arrival of eroded materials in the fluvial system.