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article imageRapid permafrost thaw an unrecognized threat to landscape

By Karen Graham     Feb 3, 2020 in Environment
A "sleeping giant" hidden in permafrost soils in Canada and other northern regions worldwide will have important consequences for global warming, says a new report by a Canadian scientist.
It's all part of a vicious cycle of climate feedback loops, and we have heard about what happens when a warming planet causes the permafrost to start thawing. When the permafrost thaws, it releases microbes that consume organic matter.
This, in turn, causes the release of CO2 and methane into the atmosphere. And it goes on - as more CO2 is released into the atmosphere, it causes even more warming and more melting and more CO2 emissions.
Permafrost covers about 24 percent of the exposed land in the Arctic that is frozen year-round, and the ice-rich permafrost soils can be up to 260 feet (80 meters) thick. But despite its name, permafrost is not always permanent. In areas further away from the Arctic Circle, permafrost can melt, even on a semi-regular basis.
File photo: A lake  which has no name and sits in the Northwest Territory s northern corner near the...
File photo: A lake, which has no name and sits in the Northwest Territory's northern corner near the community of Fort McPherson, is a victim of the region's geology and changing climate. In a dramatic example of how climate change is altering the Arctic landscape, the small northern lake has fallen off a cliff after bursting through the melting earthen rampart that restrained it. Date: Dec. 21, 2015.
Handout / Government of Northwest Territories
However, the University of Guelph scientist Merritt Turetsky and a team international researchers - in a study published in Nature Geoscience today - argue that without taking abrupt permafrost thaws into account, we’re underestimating the impact of permafrost thaw by 50 percent.
The study suggests that we are witnessing a rapid collapse of permafrost that can transform the landscape in mere months through subsidence, flooding, and landslides. "We are watching this sleeping giant wake up right in front of our eyes," said Turetsky, who holds the Canada Research Chair in Integrative Ecology, per Eurekalert.
What's going on?
Turetsky explains that the amount of carbon coming off a small range of permafrost (about 20 percent) under a rapid thaw is great enough to double the climate consequences. Some permafrost is frozen rock or even sand, and the study is not focused on that kind of permafrost.
Turetsky says the study focused on the kind of permafrost that contains a lot of water. “Where permafrost tends to be lake sediment or organic soils, the type of earth material that can hold a lot of water, these are like sponges on the landscape,” says Turetsky. “When you have thaw, we see really dynamic and rapid changes.”
Frozen water takes up more space than liquid water. So when permafrost thaws, it loses a good amount of its volume. As an analogy, think of freezing an ice cube tray of muddy water. When the tray is thawed, the muck will settle to the bottom of the tray.
“That's exactly what happens in these ecosystems when the permafrost has a lot of ice in it and it thaws,” says Turetsky. “Whatever was at the surface just slumps right down to the bottom. So you get these pits on the land, sometimes meters deep. They're like sinkholes developing in the land.”
Besides the sinkholes and other landscape alterations caused by permafrost thawing, there are far-reaching effects that are concerning. When these lands thaw and the ice turns to liquid water, trees, shrubs, and grasses die off, causing more land to feel the effects of the warming climate, causing more thawing.
Rapid thawing is also altering the natural habitats of birds and animals which call the northern reaches home. When you think of permafrost regions, you might think of featureless tundras, but most are actually boreal forests. These northern forests have recently seen an unprecedented number of wildfires.
“Much of the boreal forest burns more and more often, and when the ecosystem burns, it can actually accelerate the permafrost thaw,” says David Olefeldt of the University of Alberta, a coauthor on the paper. "Without cover from these trees to shade it, the soil warms ever more intensely."
Despite all the gloom, the researchers remain optimistic. "If we can limit human emissions, we can still curb the most dangerous consequences of climate warming. Our window for action is getting narrow, but we still have it and can make changes to save the Arctic as we know it, and the Earth's climate along with it," says Turetsky.
More about Permafrost, rapid thawing, carbon sourse, Climate crisis
 
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