New research investigated two massive landslides in the Mackenzie River basin that happened nearly a decade ago.
The two landslides in question happened on the Johnson River and the Redstone River, recorded in 2017 and 2018, respectively. Researchers call them “permafrost detachment slides”, as they determined their cause stands apart from other similar events related to permafrost thaw.
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Researchers said the slides were different in character from previously observed events – in that instead of originating from the surface, downward, these slides, in relatively thin permafrost tens of meters deep, originated from the “bottom, up”.
Scientists said that severe wildfires in the area set up the conditions for the permafrost degradation, by wiping out the organic material on the surface.
Steve Kokeji, an author of the new study, told CBC, ““About 15 to 20 years after the fire, all of these larger disturbances start to occur within these old burn areas,” Kokelj said. “That’s about the time it takes for that to permeate 20 metres into the ground.”
“It’s the warming effect on permafrost in this scenario, the warming effect of fire compounding, [and], of course, the effects of a warming climate.”
Permafrost slopes are now failing in new and unprecedented ways. We document two massive landslides (2017 and 2018) in the central Mackenzie Valley, Northwest Territories, that moved 4.5 and 18 million cubic meters of frozen ground respectively. These are among the largest contemporary permafrost failures in Canada. We term these landslides, “permafrost detachment slides” (PDSs), because they differ fundamentally from traditional permafrost mass wasting. PDSs involve warming and thaw at the base of permafrost, causing the entire frozen layer to detach and rapidly slide downslope as large cohesive blocks. Hundreds of similar failures occur across the Northwest Territories in areas where permafrost is warm (above −1°C) and thin (less than 40 m). Climate warming and wildfire work together to drive heat to depth over decades, weakening the permafrost base. Early signs of instability include gradual downslope movement, tension cracks, and surface ponding, which allow water to infiltrate and accelerate thaw at depth. Once thresholds are met, catastrophic failure can mobilize frozen material and produce valley blocking debris deposits and dammed lakes kilometers long. Exposed ice-rich scarps continue thawing, triggering secondary landslides and irreversibly reshaping the landscape. PDSs represent an unrecognized failure mechanism that poses growing hazards as permafrost warms across northern regions.
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In another related study, researchers argued that permafrost degradation, like that observed above, is not well represented in current climate models, and could add significantly to warming by 2100.
Warming-induced emissions (WIE) of greenhouse gases from natural sources are a large amplifying feedback that most climate models do not yet represent. This absence risks systematic underestimation of projected future warming and overestimation of remaining carbon budgets.
….we projected that WIE could add 0.2 °C–0.4 °C of warming by 2100 across scenarios, split roughly equally between carbon dioxide and methane, amplifying post-2020 anthropogenic warming by 20%–30%.