Talk
Changing Permafrost Landscapes

Increases in permafrost mass-wasting driven by failure at the base of permafrost in the central Mackenzie Mountain Foothills

Online pre-recorded
(Student abstract)

Author(s)

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

Hillslope mass-wasting in the extensive discontinuous permafrost zone of the central Mackenzie Mountain foothills has significantly increased in frequency and magnitude in the past 15 years. The increase in thaw-driven mass-wasting is largely a function of increasing air and ground temperatures, precipitation, and legacy thermal disturbance from forest fire activity. In contrast to retrogressive thaw slumps, which initiate and develop from the progressive top-down and lateral thaw of permafrost, we identify an increasing frequency and magnitude of deep-seated translational permafrost landslides with failure planes at depths up to 15 meters below the active layer. We identify a suite of thaw-driven processes that involve basal permafrost sliding, thaw-driven fluidized flow, and continued scarp enlargement by retrogressive failure.  Thaw-driven detachment of materials at depth produces the capacity to rapidly transport large amounts of frozen material downslope in a blocky manner, often resulting in individual disturbances covering 10s of hectares, and in some instances, damming river drainage. The downstream impacts of rapid large-scale thawing events in this discontinuous permafrost region are not sufficiently understood, but the sediment flux potential is comparable with “mega-slump” thermokarst disturbances. We employ high-resolution satellite and UAV imagery, along with repeat digital elevation models, geological observations, and electrical resistivity tomography surveys to infer that ‘bottom-up’ thaw from the base of the permafrost table is driving the initiation of these features. We present these observations, and put forward a conceptual framework outlining their setting and mechanism of failure at the base of permafrost.  Further understanding of the setting and variability of permafrost mass-wasting has implications at all scales, not least of which involves assessing thaw-induced impacts to downstream aquatic systems.