Preprints
https://doi.org/10.5194/tc-2020-218
https://doi.org/10.5194/tc-2020-218

  28 Sep 2020

28 Sep 2020

Review status: this preprint is currently under review for the journal TC.

Permafrost thaw couples slopes with downstream systems and effects propagate through Arctic drainage networks

Steven V. Kokelj1, Justin Kokoszka1,2, Jurjen van der Sluijs3, Ashley C. A. Rudy1, John Tunnicliffe4, Sarah Shakil5, Suzanne Tank5, and Scott Zolkos5,6 Steven V. Kokelj et al.
  • 1Northwest Territories Geological Survey, Yellowknife, NT, X1A 2L9, Canada
  • 2Wilfrid Laurier University, Yellowknife, NT, X1A 2L9, Canada
  • 3Northwest Territories Centre for Geomatics, Yellowknife, NT, X1A 2L9, Canada
  • 4Department of Earth Sciences, University of Auckland, Auckland, NZ
  • 5Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E3, Canada
  • 6Woods Hole Research Centre, Falmouth, MA, 02540, USA

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 slump enlargement and described the processes and thresholds coupling slopes to downstream systems; B) investigate catchment-scale patterns of slope thermokarst (thaw slumps and slides) impacts and the geomorphic implications; and C) project the propagation of effects through hydrological networks draining continuous permafrost of northwestern Canada. Power-law relationships between thaw-slump area and volume (R2 = 0.90), and thickness of permafrost thawed (R2 = 0.63), combined with the multi-decadal (1985–2018) increase in areal extent of thaw-slump disturbance show a two-order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant catchment effects are to first- and second-order streams where sediment delivery commonly exceeds stream transport capacity by orders of magnitude indicating millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates thaw-driven mass wasting directly affects over 6,760 km of stream segments, 890 km of coastline, and 1,370 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 > 5,600), impacted stream length by a factor of 7 (> 48,000 km) and defines several major impact zones to 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 the landmasses of Banks and Victoria Islands. Peel and Mackenzie Rivers are globally significant conveyors of the slope thermokarst cascade delivering effects to North America’s largest 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 renewal of post-glacial landscape evolution. Glacial legacy and the patterns of continental drainage dictate that terrestrial, freshwater and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia.

Steven V. Kokelj et al.

 
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Steven V. Kokelj et al.

Steven V. Kokelj et al.

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Short summary
We address knowledge gaps in the understanding the climate-driven amplification of slope thermokarst, the evolution of downstream linkages, and the cascade of consequences. The non-linear intensification of thaw-driven landslides in glaciated permafrost terrain of northwestern Canada has strengthened slope to stream connectivity. Primary effects to headwater systems indicate the major potential for long-term impacts and their propagation across watershed scales to coastal environments.