Arctic Permafrost Is Melting so Fast, It's Gouging Holes in the Landscape
Current estimates of carbon emissions from melting Arctic permafrost rely on a model of a gradual melt. New research has found abrupt thawing of permafrost which means carbon emissions estimates should be doubled. The rate at which permafrost is thawing in the Arctic is gouging holes in the landscape, according to a new study published in the journal Nature Geoscience.
The UN's Intergovernmental Panel on Climate Change has not considered the phenomenon of thermokarst — the degraded land ravaged by an abrupt thaw. When the permafrost that supports the soil disappears, then hillsides collapse and enormous sinkholes suddenly appear, as Wired reported. The effect runs through meters of permafrost and takes a matter of months or a few years. That upends the traditional models of permafrost thawing, which look at a few centimeters of permafrost melt over several decades. The rapid change to the permafrost shocks the landscape, causing an enormous release of carbon.
"The amount of carbon coming off that very narrow amount of abrupt thaw in the landscape, that small area, is still large enough to double the climate consequences and the permafrost carbon feedback," said study lead author Merritt Turetsky, of the University of Guelph and University of Colorado Boulder, as Wired reported.
The researchers found that abrupt thawing will happen in less than 20 percent of the permafrost zone, "but could affect half of permafrost carbon through collapsing ground, rapid erosion and landslides," the authors wrote in the study.
Not only does an abrupt thaw release carbon, but it also releases a tremendous amount of methane, a potent greenhouse gas. So, while only 5 percent of the permafrost may experience abrupt thaw at one time, the emissions will be equal to a much larger area going through a gradual thaw. This can rapidly change the landscape drastically.
"Forests can become lakes in the course of a month, landslides occur with no warning, and invisible methane seep holes can swallow snowmobiles whole," Turetsky said in a statement from the University of Colorado Boulder. "Systems that you could walk on with regular hiking boots and that were dry enough to support tree growth when frozen can thaw, and now all of a sudden these ecosystems turn into a soupy mess," Turetsky added.
The most worrisome permafrost is the type that holds a lot of water because frozen water takes up more space than water. When it thaws it loses a lot of volume. "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," Turetsky said, as Wired reported. "When you have thaw, we see really dynamic and rapid changes."
Turetsky has witnessed the rapid change in the course of the study. She has seen the melting submerge equipment she has placed to check temperature and methane.
"When you come back in, it's a lake and there's three meters of water at the surface. You have to probably say goodbye to your equipment," she told Wired. "Essentially, we're taking terra firma and making it terra soupy."
The researchers realized that the thermokarst they observed was absent in climate emissions models and tried to account for its output.
"The impacts from abrupt thaw are not represented in any existing global model and our findings indicate that this could amplify the permafrost climate-carbon feedback by up to a factor of two, thereby exacerbating the problem of permissible emissions to stay below specific climate change targets," said David Lawrence, of the National Center for Atmospheric Research and a coauthor of the study in a press release.
The paper shows the sudden need to include permafrost thaw in all climate models.
"We can definitely stave off the worst consequences of climate change if we act in the next decade," Turetsky said in a press release. "We have clear evidence that policy is going to help the north and thus it's going to help dictate our future climate."
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