Thaw-driven mass wasting couples slopes with downstream systems, and effects propagate through Arctic drainage networks

Abstract

Abstract. The intensification of thaw-driven mass wasting is transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Within the context of recent, rapidly evolving climate controls on the geomorphology of permafrost terrain, we (A) quantify three-dimensional retrogressive thaw slump enlargement and describe the processes and thresholds coupling slopes to downstream systems, (B) investigate catchment-scale patterns of slope thermokarst impacts and the geomorphic implications, and (C) map the propagation of effects through hydrological networks draining permafrost terrain of northwestern Canada. Power-law relationships between retrogressive thaw slump area and volume (R2=0.90), as well as the thickness of permafrost thawed (R2=0.63), combined with the multi-decadal (1986–2018) increase in the areal extent of thaw slump disturbance, show a 2 order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant effects are to first- and second-order streams where sediment delivery, often indicated by formation of recent debris tongue deposits, commonly exceeds the transport capacity of headwater streams by orders of magnitude, signaling centennial- to millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates that thaw-driven mass wasting directly affects over 5538 km of stream segments, 889 km of coastline, and 1379 lakes in the 994 860 km2 study area. Downstream propagation of slope thermokarst indicates a potential increase in the number of affected lakes by at least a factor of 4 (n>5692) and impacted stream length by a factor of 8 (>44 343 km), and it defines several major impact zones on lakes, deltas, and coastal areas. Prince of Wales Strait is the receiving marine environment for greatly increased sediment and geochemical fluxes from numerous slump-impacted hydrological networks draining Banks Island and Victoria Island. The Peel and Mackenzie rivers are globally significant conveyors of the slope thermokarst cascade, delivering effects to North America's largest Arctic delta and the Beaufort Sea. Climate-driven erosion of ice-rich slopes in permafrost-preserved glaciated terrain has triggered a time-transient cascade of downstream effects that signal the rejuvenation of post-glacial landscape evolution. Glacial legacy, ground-ice conditions, and continental drainage patterns dictate that terrestrial, freshwater, coastal, and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia.

Vegetal Undercurrents—Obscured Riverine Dynamics of Plant Debris

“…In high‐latitude environments, thaw‐driven destabilization of soils and sediments increasingly shapes Arctic landscapes (Nitze et al., 2018 ). These thermo‐erosional mass wasting events, including gullies, active layer detachment slides, and retrogressive thaw slumps actively couple hillslopes with aquatic systems, entraining a wide range of vegetation and permafrost‐derived POC (Bröder et al., 2021 ; Kokelj et al., 2021 ; Shakil et al., 2020 ).…”

“…On the other hand, elevated temperature conditions may promote the accelerated decay of plant detritus prior to its transfer to the aquatic system. While increased precipitation will further the efficacy of surface runoff (Anderson et al., 2018 ; Bintanja et al., 2020 ), the loss of permafrost will both enhance physical erosion (e.g., Bröder et al., 2021 ) and hydrological connectivity in soils, resulting in heightened discharges of water, nutrients (Doxaran et al., 2015 ; Drake et al., 2018 ; McClelland et al., 2016 ; Rood et al., 2017 ; Tank et al., 2016 ), and sediments to the Arctic Ocean (Kokelj et al., 2021 ; Wild et al., 2019 ). In deltaic settings, permafrost thaw and changes in ice thickness will fundamentally affect Arctic delta morphology, the dispersal, and retention of flow and sediment.…”

We Must Stop Fossil Fuel Emissions to Protect Permafrost Ecosystems

“…In areas with ground ice, soil warming often triggers abrupt surface collapse, mass wasting, and coastal erosion (Kokelj and Jorgenson, 2013;Olefeldt et al, 2016;Grotheer et al, 2020;Angelopoulos et al, 2021). These thermokarst processes have a wide range of consequences depending on landscape position and soil characteristics (Mu et al, 2020a;Turetsky et al, 2020;Yang et al, 2021), including soil warming, GHG release or uptake, and delivery of sediment and solutes to aquatic ecosystems (Anthony et al, 2014;Abbott et al, 2015;Farquharson et al, 2019;Kokelj et al, 2021;Wologo et al, 2021;Yang et al, 2021). Subsidence can result in complex changes in soil moisture, affecting the type and amount of GHGs produced, further complicating estimates of permafrost climate feedbacks (Lupascu et al, 2013;Lawrence et al, 2015;Boike et al, 2016;Schuur et al, 2022).…”

“…Pierre et al, 2018;Rodríguez-Cardona et al, 2020;Abbott et al, 2021b). For example, in the western Canadian Arctic, mass wasting along fluvial networks has increased two orders of magnitude from 1986-2018, creating sedimentary deposits that will cascade through rivers and lakes to the Arctic Ocean for decades to millennia (Kokelj et al, 2021). Understanding and preventing changes in water chemistry and river discharge are particularly important for the Tibetan Plateau, which provides drinking and agricultural water for 1.4 billion people (Yao et al, 2018;Mu et al, 2020b;Gao et al, 2021).…”

Retrogressive thaw slumps in the Alaskan Low Arctic may influence tundra shrub growth more strongly than climate

“…Increased vertical and lateral growth of shrubs can also drive changes to ecosystem feedback and food webs (Euskirchen et al, 2009; Myers‐Smith & Hik, 2013; Tape et al, 2018). Retrogressive thaw slump activity is likely to increase in vulnerable areas with warming (Kokelj et al, 2015; Kokelj et al, 2021; Luo et al, 2019; Nitze et al, 2018) and may lead to tall shrub communities that can persist for many decades (Lantz et al, 2009). Quantifying shrub growth response to interannual climate variation in RTS versus undisturbed tundra is therefore important to understand the greening of the Arctic that is currently underway (Myers‐Smith et al, 2020).…”