Changing Permafrost Landscapes

Initial investigations of degrading dendritic peat plateaus in the central Mackenzie Valley, Northwest Territories

Online pre-recorded
(Student abstract)


A. Chiasson (Presenting)
University of Alberta
B. Andersen
University of Alberta
A. Alvarez
University of Alberta
S.V. Kokelj
Northwest Territories Geological Survey, GNWT
J. van der Sluijs
Northwest Territories Centre for Geomatics, GNWT
A.C.A. Rudy
Northwest Territories Geological Survey, GNWT
D. Froese
University of Alberta

Peat plateaus dissected by dendritic fluvial and fen networks are common landforms in the central Mackenzie Valley, Northwest Territories. These networks tend to be associated with sloping site conditions (up to ~ 3m per km), and are largely developed on moraine and glaciolacustrine sediments. These sites are often covered by tussocks, reindeer lichens (Cladonia sp.) and varying cover of open black spruce (Picea mariana). Field investigation of 3 sites in 2021 showed that peat thicknesses were ~ 2m with structureless pore ice, that was overlaying several metres of ice-rich diamict or glaciolacustrine sediments. Electrical resistivity tomography profiles indicate that permafrost is typically thin in these areas (5-12 m), and through-going taliks forming the channel network are common, and increase in frequency downslope. The taliks appear to extend under the margins of the peat plateaus adjacent to the taliks, and are commonly captured to form the dendritic network. There seems to be little evidence for surface disturbances, and local depressions on the surface appear to extend into the underlying ice-rich sediments, and are very recent based on flooded black spruce (Picea mariana) and reindeer lichens (Cladonia sp.) within ponds. We hypothesize that these are slowly expanding thaw networks, likely driven by basal permafrost thaw near taliks.