Global warming is causing a 60-fold increase in permafrost landslides. Time is of the essence. We need effective, immediate climate policies now.
Retrogressive thaw slump, Herschel Island, Yukon, Canada. Credit: National Geographic Image Collection / Alamy Stock Photo.
However, the thawing of these perennially frozen soils also risks making a mark on the land surface itself, causing landslides known as “retrogressive thaw slumps”.
A retrogressive thaw slump (RTS) is a landslide that can occur only in permafrost areas. It develops when the ice within the soil melts rapidly, leaving the soil weakened and unstable. Where this happens on a slope, the instability can result in a landslide.
We call these landslides “retrogressive” because the headscarp – the steep exposed soil face at the top of the landslide – progressively retreats upslope after the initial slumping. They are “thaw” slumps because they are caused by the thawing of ice in the permafrost. And they are “slumps” because that’s the term most commonly used for bowl-shaped landslides.
An RTS resembles a sand pit dug out of a slope, with melting ice present around its upper edge, which constantly collapses. Mud and water then collects in the bottom of the landslide “pit”, making a mud slurry that eventually flows away into rivers, lakes or the ocean. Once started, an RTS can remain active and grow in size for many years as the headscarp progressively moves upslope. MORE
Research has shown that the Arctic region is currently warming around twice as fast as the global average, and this is causing permafrost—or frozen soils—to thaw, often for the first time in thousands of years.
“As the temperature of the ground rises above freezing, microorganisms break down organic matter in the soil,” the authors wrote in the article. “Greenhouse gases—including carbon dioxide, methane and nitrous oxide—are released into the atmosphere, accelerating global warming.”
This is particularly worrying given that Arctic permafrost holds twice as much carbon as the entire atmosphere—almost 1,600 billion tonnes, the researchers say. MORE