Remote Sensing and Biogeochemical Analyses of Sediments from the Willow River Catchment, NT, Canada Using Landsat Imagery and Field Samples from 2021

The goal of this research is to understand how climate-driven permafrost thaw and mass-wasting processes are reshaping sediment transport pathways and biogeochemical conditions in the Willow River catchment on the Peel Plateau, Northwest Territories, Canada. To investigate these changes, we combined remote sensing analyses with field-based sediment sampling. Remote sensing analyses were conducted in ArcGIS using Landsat 4/5, 7, and 8 imagery to assess multi-decadal trends in thaw-driven mass-wasting features, surface disturbance, and slope-to-stream connectivity. Sediment data were collected from geomorphically active environments across the catchment. Bulk samples were taken from permafrost headwalls (active layer, Holocene-origin permafrost, and Pleistocene-origin permafrost), eroding cutbanks, streambeds, and a landslide. Core samples were collected from the aggrading surface of Willow Lake, nearby delta lakes, and forested alluvial settings. Samples were analyzed for organic carbon, nitrogen, sulfur, LOI, mineralogy (XRD), grain size, radiocarbon (¹⁴C), cations, density, and magnetic susceptibility to characterize sediment provenance and post-depositional processes. Results show a rapid, non-linear increase in thaw-driven mass-wasting features, with 3.8-, 9.2-, and 16.3-fold increases in their number, size, and density. These changes enhanced sediment delivery to fluvial systems and contributed to a rerouting of the Willow River into Willow Lake. Turbidity increased in lakes along the new inflow channel and declined along the abandoned channel. Sediment cores show shifts in material provenance and a coarsening-upward sequence consistent with recent delta progradation. Thermal data indicate new permafrost formation within deltaic deposits and upward aggradation of the permafrost table in forested areas due to increased overbank sedimentation. Overall, the data demonstrate that mobilization of permafrost-preserved glacial materials is transforming slope environments, river networks, and depositional basins, with implications for the redistribution and potential sequestration of organic carbon as sediments move through the system.