The effects of global climate change are especially acute in permafrost environments of Canada’s North. Accelerated changes in temperature and increases in precipitation are resulting in impacts to northern landscapes. Permafrost degradation of ice-rich slopes can result in the development of retrogressive thaw slumps and other types of mass wasting, which can result in the transport of previously frozen materials into nearby aquatic systems. The introduction of these thaw derived materials can have biogeochemical implications at scales ranging from global (the carbon cycle) to local (within-stream ecological function) and can cascade across watershed scales.
The Willow River catchment (near Aklavik, NT) has experienced a major increase in thaw-driven geomorphic activity over the past several decades, which has caused the main river channel to divert and deposit sediments within Willow Lake, causing the lake to infill. This project focuses on identifying the biogeochemical changes to the Willow River catchment through a temporal and spatial lens. Specifically, this study aims to understand how the amount and composition of materials flowing downstream have changed over the past several decades as thaw-driven geomorphic activity has accelerated over time, as well as investigating the reactivity and downstream progression of thermokarst-derived materials.
In spring and summer 2021, a team of academics and local land users worked together to collect a series of sediment cores to investigate sediment organic content and composition, as well as mineral composition of terminally deposited materials. A series of cores were collected along a transect towards to apex of the aggrading delta within Willow Lake, as well as along the cut bank of the Willow River that feeds into Willow Lake, the shoreline along Willow Lake, the channel within Willow Lake, and from a series of adjacent lakes connected to Willow Lake. To capture source composition and infer transformation in-stream, a series of “end-member” samples were collected from eroding thermokarst and landslide features, as well as from streambanks along the Willow River channel. Additionally, bulk water samples were collected to assess changes in water chemistry and suspended materials as they move through the system. All samples collected are currently being processed and analyzed at the University of Alberta. To complement this array of temporal and spatial data, remote sensing analyses are being conducted to understand the evolution of thaw slumps and their impacts on stream networks in the Willow River catchment over the past several decades.
Understanding changes in the reactivity of thermokarst-derived materials as they propagate through fluvial networks will provide insight into how permafrost thaw is impacting the ecological functioning of downstream systems and the degree to which within-stream mineralization of permafrost-derived organic carbon affects the broader carbon cycle. The results of this research will directly impact nearby communities such as Aklavik, NT, by providing valuable information on the historic and current effects of permafrost thaw on aquatic systems and water resources, which will integrate with local knowledge of the land to better inform and prepare local communities for future changes in climate.