Assessment of the sediment and associated nutrient/contaminant continuum, from permafrost thaw slump scars to tundra lakes in the western Canadian Arctic

Abstract

Within the Canadian Arctic, vast areas of previously frozen sediments and carbon are being released into aquatic ecosystems via the occurrence of permafrost thaw and retrogressive thaw slumps (RTSs). While knowledge of mass wasting RTS processes are more advanced, the significance of exposed retrogressive thaw slump scars (RTSSs) at various phases of stabilization to yield additional large quantities of ecologically relevant sediment to lakes and rivers is not well constrained. Using laboratory simulation (linked rainfall and lake flow dynamics), RTS sediments were investigated to assess the sediment continuum from the terrestrial RTSSs to depositional zones within two Arctic tundra lakes. Using an estimate of 30% of the RTSS areas contributing sediment under hypothetical 20-and 100-year rainfall events, up to 598 and 997 kg hr À1 of RTSS sediment washoff was projected respectively. Eroded particle size, regardless of lake or initial bulk RTSS size distribution, was dominated by individual clay particles (<5 μm) that were winnowed from the RTSS surface sediment. Given this is the most biogeochemical relevant fraction, it has the potential for significant ecological impact on the lakes. This deposited fine sediment was found to be very unstable with a critical shear stress for erosion close to that of the critical shear for deposition (0.05 Pa). As such, wave energy is expected to have an impact on remobilization of fine sediments and associated compounds with concomitant implications for lake-ecosystem health.

Effects of Ground Subsidence on Permafrost Simulation Related to Climate Warming

“…The volume of ice within permafrost can exceed the volume of natural soil pores because of ice wedges, segregation ice or ice lenses. Ground subsidence, which occurs as a consequence of ground ice melting, has been exacerbated in permafrost regions worldwide in recent years [9][10][11]. Changes to landforms as a result of ground subsidence can damage the foundations of buildings and lead to irreversible ecological changes [12][13][14] but also influence the trajectories of subsequent permafrost changes [15].…”

Sensitivity of Erosion‐Rate in Permafrost Landscapes to Changing Climatic and Environmental Conditions Based on Lake Sediments From Northwestern Alaska

“…Erosion can also change the surface topography and thus modify the distribution of solar radiation across the landscape and change surface and subsurface hydrology (e.g., Liljedahl et al., 2016; Turetsky et al., 2020; van Huissteden, 2020). Further, eroded soil particulates and nutrients transported into the Arctic aquatic systems (i.e., rivers, lakes, deltas, oceans) can degrade water quality (e.g., Bilotta & Brazier, 2008; Droppo et al., 2021; Levenstein et al., 2020), harm aquatic ecosystems (Chin et al., 2016; Vucic et al., 2020), and change the partitioning of carbon stocks between terrestrial and aquatic systems (Fuchs et al., 2020; Li et al., 2021; Rowland et al., 2010). Despite the potential influence of these processes on the Arctic system, the relations between erosion‐rate and environmental conditions (e.g., climate, permafrost, vegetation, wildfires, hydrology) remain largely unquantified (Lane, 2012; Li et al., 2021; Pelletier et al., 2015; Rowland et al., 2010; Spencer & Lane, 2016), impeding predictions of the Arctic system's response to future changes.…”