SEDIMENT PRODUCTION AND TRANSPORT PROCESSES IN AN ARCTIC WATERSHED-FAN SYSTEM UNDERGOING CLIMATE CHANGE

Arctic landscapes are among the most vulnerable on Earth to climate change, largely due to the rapid degradation of permafrost. In steeper bedrock-dominated terrains, warming permafrost can lead to increased bedrock damage and sediment production due to enhanced temperature conditions for frost-driven cracking events. This, in turn, can amplify the delivery of sediment to channels by debris flow and fluvial processes. However, there is a fundamental lack of data on current rates of sediment production and transport in Arctic watersheds, making it impossible to predict the transient responses and rates of periglacial processes under future climate change.

To begin to address this gap, we are conducting a multi-year field-based study of the Black Mountain catchment in the Aklavik Range (Canada). This site was chosen due to the presence of an alluvial fan at the base of the catchment, providing a closed system where we can consider how changing temperatures influence physical weathering and transport. Recent work has focused on documenting sediment transport conditions on the fan, including active fluvial bedload transport as well as several small debris flows and landslides. Following a snowmelt-induced runoff event of ~0.2 mm/hr across the fan, we estimated sediment fluxes of ~0.04 m³/hr. Under bankfull conditions, we estimate runoff rates between ~0.1 to ~10 mm/hr and corresponding sediment fluxes of ~0.3 to ~550 m³/hr.

While these events have yielded modern-day fluvial and mass flow transport rates on a periglacial alluvial fan, surficial and sedimentological mapping suggests that accelerated warming is increasing sediment supply to the fan due to frost cracking. This is leading to fan aggradation and potentially increased debris flow activity. As such, current work is focused on estimating sediment production rates using a pre-existing physically based frost cracking model.