Quirks & Quarks

Permafrost landslides are eating great swathes of Arctic landscape

Sixty square kilometres of land has turned to muck on Banks Island

Sixty square kilometres of land has turned to muck on Banks Island

A thaw slump on Banks Island. New research has shown that these landscape altering events have become vastly more common in the last two decades (Professor Antoni G. Lewkowicz)

A Canadian permafrost researcher has discovered that vast swaths of Canadian Arctic landscape are melting and sliding away as temperatures rise in the Arctic.

Antoni Lewkowicz, a professor of geography at the University of Ottawa, led a team that found a massive increase in a particular kind of landslide called "retrogressive thaw slumps," on Banks Island, the westernmost island in the Arctic.

They published their study this week in the journal Nature Communications

These slow-motion landslides slides happen on relatively low-angle slopes as permafrost melts in the Arctic summer.  The ice provides structure for the overlying soil, and as the ice melts, the soil simply collapses into a muddy mess that slides down the slope. 

A typical slump like this might affect a front 100 metres long, and continue through the summers over many years, retreating up the slope as the land collapses downhill.

The team used Google Earth Engine Timelapse to count the increase in the number of these slumps from 1984 to to 2016.  This tool provides a way to look at sequences of Landsat satellite images to provide a time-lapse picture of landscape changes.  Initially the work began as a student assignment until they realized how significant the changes were.

Google Earth Timelapse video of a 2.5km wide are of thaw slumping on Banks Island

The team discovered that over the last two decades that these landslides went from uncommon to incredibly frequent - increasing from about 63 in 1984 to more than 4,000 by 2013.

They calculate that on the eastern side of Banks Island, where they saw most of these slumps occurring, that an area of about 60 square kilometres had been affected. This would represent about 100 million tons of permafrost ice that had melted away.

The impacts on the landscape are likely to have knock-on effects on water systems and probably on wildlife as well. Lewkowicz said the satellite imagery showed streams and lakes becoming cloudier as silt from the dissolving landscape clogged watercourses.

Banks Island is also home to an Inuvialuit community, and Lewkowicz says the people there are certainly being impacted by the changes to the land they live on.

Lewkowicz only looked at Banks Island in this particular study, and he makes it clear that this is not happening all over the Arctic. 

These landslides seem only to affect certain kinds of ancient permafrost landscapes that contain ice from the last ice-age.  But in ongoing, as yet unpublished work, he says that the team is seeing similar increases in slumping on nearby Victoria Island.

Video provided by the University of Ottawa


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