Permafrost is thawing so fast, in can turn a forest into a lake in the course of one month. Flickr / CC BY-NC 2.0
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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Permafrost Is Thawing So Fast, It’s Gouging Holes in the Arctic
Normally, these terrains of frozen soil thaw gradually. But in some places, it’s thawing so abruptly that landscapes are collapsing in on themselves.
It’s perhaps the best known and more worrisome of climate feedback loops: As the planet warms, permafrost—landscapes of frozen soil and rock—begins to thaw. And when it does, microbes consume organic matter, releasing CO2 and methane into the atmosphere, leading to more warming, more thawing, and even more carbon emissions.
But here’s something you’ve probably never heard of, and it’s something not even the UN’s Intergovernmental Panel on Climate Change has really considered: thermokarst. That’s the land that gets ravaged whenever permafrost thaws rapidly. As the ice that holds the soil together disappears, hillsides collapse and massive sinkholes open up. Climate scientists have been working gradual permafrost thaw into their models—changes that run centimeters deep over decades or centuries. But abrupt permafrost thaw happens on the scale of meters over months or years. That shocks the surrounding landscape into releasing potentially even more carbon than would have if it thawed at a more leisurely pace.
Today in the journal Nature Geoscience, researchers argue that without taking abrupt thaws into account, we’re underestimating the impact of permafrost thaw by 50 percent. “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,” says study lead author Merritt Turetsky, of the University of Guelph and University of Colorado Boulder.
Less than 20 percent of northern permafrost land is susceptible to this kind of rapid thaw. Some permafrost is simply frozen rock, or even sand. But the kind we’re worried about here contains a whole 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.”
That’s because frozen water takes up more space than liquid water. When permafrost thaws, it loses a good amount of its volume. Think of it like thawing ice cubes made of water and muck: If you defrost the tray, the greenery will sink to the bottom and settle. “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.”
“Essentially, we’re taking terra firma and making it terra soupy,” Turetsky adds.
As the earth turns to soup, the landscape begins to scar. The process is so rapid and so violent, Turetsky says, that sometimes when she returns to a site she’s monitoring to check her temperature and methane sensors, she’ll find they are gone. “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 says.
When these lands thaw, they play host to a number of processes. As ice turns to liquid water, trees flood and die off. Thus more light reaches the soil, further accelerating thawing. This is in contrast to gradual thaw, when the plant community largely stays the same as the ice thaws. Defrosted soil at the surface gets thicker and thicker, but it doesn’t catastrophically collapse.
In addition, when you think of permafrost regions, you might think of featureless tundras, but most is actually boreal forest. 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 University of Alberta, coauthor on the paper. Without cover from these trees to shade it, the soil warms ever more intensely.
Abrupt warming also exacerbates emissions from permafrost. In a gradual thaw, the warming top layers of the soil open up to hungry microbes, which consume nutrients and give off CO2. “In the summer, permafrost—the top layer at least—thaws, and then cracks can build,” says Northern Arizona University biogeochemist and plant ecophysiologist Christina Schaedel, who collaborates with the authors of this new paper, but wasn’t involved in the work. In the fall it freezes back up, creating a cycle in which soil layers get mixed down to the bedrock, concentrating carbon at the bottom. “With abrupt thaw, you’re exposing deeper layers to much warmer temperatures, and deep layers in permafrost can contain very high amounts of carbon,” Schaedel says.
This can become particularly problematic from an emissions standpoint if the collapsed land forms a pond of water with low oxygen content, and with a layer of rich carbon at the bottom. The microbes that thrive in this kind of environment produce methane as a byproduct, a far more potent greenhouse gas than CO2.
Here’s an important consideration: When permafrost melts abruptly, it doesn’t just release carbon and then retire. That ecosystem can heal and begin sequestering carbon again. If the land has thawed, then collapsed and become inundated with water, new trees can’t grow. Instead, that ecosystem is likely to become dominated by mosses and grass-like sedges. Because the plant material is waterlogged, decomposition actually slows as it forms peat—thick, mucky, layers of organic matter.
“So this rapid post-thaw peat accumulation that happens is eventually how it recovers some of the carbon that was lost,” says USGS research geologist Miriam Jones, coauthor on the new paper. “But I will say that in the permafrost, carbon has accumulated over millennia. And so upon thaw, it’s rapidly lost within years to decades.”
It will take centuries or millennia, depending on the ecosystem, to sequester all that carbon again. And of course in the Arctic, which is warming twice as fast as the rest of the planet, the composition of vegetal species that make up some of its ecosystems are transforming, in turn changing how they sequester carbon.
The more closely scientists can parse what happens when permafrost thaws rapidly, the better they account for how these landscapes emit greenhouse gases—and eventually sequester some, too. The bad news is, the emissions could be the equivalent of an entire industrialized nation’s greenhouse output. The better news is, it won’t be as much as humanity’s global toll. “Even though these are hot spots of carbon release, it’s going to take decades for those hot spots to become large enough to seriously impact the climate system,” says Turetsky. “But this is still something we need to take seriously.”
And it’s something that needs far more research. Any climate modeling comes with inherent uncertainties—there’s no way to perfectly represent such complex systems. The uncertainty here is projecting how much land might succumb to abrupt thawing, says University of Alaska Fairbanks permafrost geophysicist Vladimir Romanovsky, who wasn’t involved in the work. Scientists have only begun to study these rapid thaw events, which often happen at extremely small scales.
“It’s very difficult in this particular case to use the past to predict the future,” says Romanovsky. “That’s understandable, and definitely there are some ways to try to narrow down this uncertainty. But that uncertainty will be there for forever, because of the limitation of all the models to predict this process in the future, in particular the entire area of permafrost existence.”
What’s clear, though, is that ecosystems in the Arctic are literally in upheaval. And the faster we cut emissions, the less they will suffer.
Matt Simon is a science journalist at WIRED, where he covers biology, robotics, cannabis, and the environment. He’s also the author of Plight of the Living Dead: What Real-Life Zombies Reveal About Our World—And Ourselves, and The Wasp That Brainwashed the Caterpillar, which won an Alex Award.
Arctic permafrost thaw plays greater role in climate change than previously estimated
Published: Feb. 3, 2020 • By Kelsey Simpkins
An Arctic forest struggles to survive in a lake created by abrupt permafrost thaw. (Credit: David Olefeldt)
Merritt Turetsky. (Credit: INSTAAR)
Abrupt thawing of permafrost will double previous estimates of potential carbon emissions from permafrost thaw in the Arctic, and is already rapidly changing the landscape and ecology of the circumpolar north, a new CU Boulder-led study finds.
Permafrost, a perpetually frozen layer under the seasonally thawed surface layer of the ground, affects 18 million square kilometers at high latitudes or one quarter of all the exposed land in the Northern Hemisphere. Current estimates predict permafrost contains an estimated 1,500 petagrams of carbon, which is equivalent to 1.5 trillion metric tons of carbon.
The new study distinguishes between gradual permafrost thaw, which affects permafrost and its carbon stores slowly, versus more abrupt types of permafrost thaw. Some 20% of the Arctic region has conditions conducive to abrupt thaw due to its ice-rich permafrost layer. Permafrost that abruptly thaws is a large emitter of carbon, including the release of carbon dioxide as well as methane, which is more potent as a greenhouse gas than carbon dioxide. That means that even though at any given time less than 5% of the Arctic permafrost region is likely to be experiencing abrupt thaw, their emissions will equal those of areas experiencing gradual thaw.
This abrupt thawing is “fast and dramatic, affecting landscapes in unprecedented ways,” said Merritt Turetsky, director of the Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder and lead author of the study published today in Nature Geoscience. “Forests can become lakes in the course of a month, landslides occur with no warning, and invisible methane seep holes can swallow snowmobiles whole.”
Abrupt permafrost thaw can occur in a variety of ways, but it always represents a dramatic abrupt ecological shift, Turetsky added.
“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 said.
Why thawing permafrost matters
Permafrost contains rocks, soil, sand, and in some cases, pockets of pure ground ice. It stores on average twice as much carbon as is in the atmosphere because it stores the remains of life that once flourished in the Arctic, including dead plants, animal and microbes. This matter, which never fully decomposed, has been locked away in Earth’s refrigerator for thousands of years.
As the climate warms, permafrost cannot remain frozen. Across 80 percent of the circumpolar Arctic’s north, a warming climate is likely to trigger gradual permafrost thaw that manifests over decades to centuries.
But in the remaining parts of the Arctic, where ground ice content is high, abrupt thaw can happen in a matter of months – leading to extreme consequences on the landscape and the atmosphere, especially where there is ice-rich permafrost. This fast process is called “thermokarst” because a thermal change causes subsidence. This leads to a karst landscape, known for its erosion and sinkholes.
Turetsky said this is the first paper to pull together the wide body of literature on past and current abrupt thaw across different types of landscapes.
Top: Aerial image of interspersed a permafrost peatland in Innoko National Wildlife Refuge in Alaska interspersed with smaller areas of thermokarst wetlands. (Credit: Miriam Jones, U.S. Geological Survey) Bottom: A massive thaw slump on the Yedoma coast of the Bykovsky Peninsula is inspected by an Alfred Wegener Institute permafrost team. (Credit: Guido Grosse, Alfred Wegener Institute)
The authors then used this information along with a numerical model to project future abrupt thaw carbon losses. They found that thermokarst always involves flooding, inundation, or landslides. Intense rainfall events and the open, black landscapes that result from wildfires can speed up this dramatic process.
The researchers compared abrupt permafrost thaw carbon release to that of gradual permafrost thaw, trying to quantify a “known unknown.” There are general estimates of gradual thaw contributing to carbon emissions, but they had no idea how much of that would be caused by thermokarst.
They also wanted to find out how important this information would be to include in global climate models. At present, there are no climate models that incorporate thermokarst, and only a handful that consider permafrost thaw at all. While large-scale models over the past decade have tried to better account for feedback loops in the Arctic, the Intergovernmental Panel on Climate Change (IPCC)’s most recent report only includes estimates of gradual permafrost thaw as an unresolved Earth system feedback.
“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 (NCAR) and a coauthor of the study.
The findings bring new urgency to including permafrost in all types of climate models, along with implementing strong climate policy and mitigation, Turetsky added.
“We can definitely stave off the worst consequences of climate change if we act in the next decade,” said Turetsky. “We have clear evidence that policy is going to help the north and thus it’s going to help dictate our future climate.”
Other coauthors on the paper include researchers from the University of Guelph, Brigham Young University, the United States Geological Survey, University of Alaska Fairbanks, University of Alberta, Northern Arizona University, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, University of Potsdam, Stockholm University, Lawrence Berkeley National Laboratory, and the National Center for Atmospheric Research.
The Guardian | Oliver Milman The pace of sea level rise accelerated at nearly all measurement stations along the US coastline in 2019, with scientists warning some of the bleakest scenarios for inundation and flooding are steadily becoming more likely. Of 32 tide-gauge stations in locations along the vast US coastline, 25 showed a clear acceleration in sea level rise last year, according to researchers at the Virginia Institute of Marine Science (Vims). The selected measurements are from coastal locations spanning from Maine to Alaska. About 40% of the US population lives in or near coastal areas. The gathering speed of sea level rise is evident even within the space of a year, with water levels at the 25 sites rising at a faster rate in 2019 than in 2018. The highest rate of sea level rise was recorded along the Gulf of Mexico shoreline, with Grand Isle, Louisiana, experiencing a 7.93mm annual increase, more than double the global average. The Texas locations of Galveston and Rockport had the next largest sea level rise increases. Generally speaking, the sea level is rising faster on the US east and Gulf coasts compared with the US west coast, partially because land on the eastern seaboard is gradually sinking.