Permafrost, as its name implies, should be permanently frozen soil; however, that’s no longer the case. USGS researchers are looking into how these carbon-rich storage systems in northern regions, like Alaska, are changing, and what those changes mean for the rest of the world.
A disappearing act in Alaska
On a cool August morning almost a decade ago, Miriam Jones found herself in Alaska, standing in a forest filled with seemingly tipsy trees.
Although the leaning, centipede-like black spruce trees looked as if they had enjoyed boozy spirits soon before Jones’ arrival, their story wasn’t so lively. Rather, they leaned because they were literally standing on thawing soil.
Underneath much of Alaska’s forests sits permafrost, or permanently frozen soil. “Permafrost is ground that stays frozen year-round for at least two consecutive years,” Jones, a research geologist with the U.S. Geological Survey, said. Permafrost also happens to store a lot of carbon – 1,400 billion metric tons of it- which is more carbon than has ever been released by humans through fossil fuel combustion. “Most permafrost has been frozen for the last several thousand years, even up to hundreds of thousands of years,” Jones said.
However, that’s starting to change. As the climate warms and permafrost thaws, the atmosphere could get a major injection of carbon dioxide and methane, both powerful greenhouse gases.
Permafrost thaw is a key part of the Administration’s 2022-2026 Arctic Research Plan, which aims to improve the collective impacts of federal agencies in Arctic research. USGS scientists, like Jones, inform and support the Plan with their research.
To better understand how permafrost is changing, Jones digs up long, skinny tubes of the frozen soil near the “Drunken Forests” to look for clues to how it formed and what might happen to it in the future. Although her first trip was a decade ago, she’s been back a few times, often returning home with a frozen time capsule to study.
“Permafrost thaw could really change how we approach infrastructure development in the Arctic,” Jones said, “Not to mention the global impact to climate.”
Permafrost’s prowess on land
A bridge that crosses a creek once filled with golden nuggets is sinking.
Anvil Creek was famous for its treasure during the Alaskan gold rush in the late 1890s, but since then, has sat under a bridge that’s part of the 70-mile-long Nome-Teller Road. This rural highway stretches over 70 miles of remote tundra and links the city of Nome to the Inupiat town of Teller, only 55 miles away from Russia.
Permafrost "can cause a lot of damage to our infrastructure when it thaws,” the Alaska Department of Transportation and Public Facilities states on its website, impacting structures like the bridge over Anvil Creek.
The department tries to avoid building on permafrost, although that isn’t always an option because the frozen soil hides under 85% of Alaska. Officials can remove the permafrost and replace it with stable material or use techniques that help keep the ground frozen. For instance, the department installed foam board insulation on top of the Dalton Highway near Alaska’s North Slope to keep it cool during the summer. “The flip side is that it keeps the cold winter out as well, which prevents the cooling that helps to keep the permafrost cold,” the department says. However, these options are expensive and don’t always work.
Permafrost thaw is also causing coastal erosion, creating dramatic landscapes and forcing some Alaskan residents to relocate their homes.
Since the early 2000s, coastal permafrost erosion in the Arctic has increased at 13 of 14 study sites, with observational data extending back approximately 50 years. The erosion coincides with warming temperatures, sea ice reduction, and permafrost thaw.
Permafrost’s perturbations to the atmosphere
“The Arctic is heating up faster than every other place on Earth,” Mark Waldrop, a research scientist at USGS, said.
Climate change is accelerated in northern regions because of positive feedback effects. For example, as sea ice melts, we lose a bright, white surface that reflects heat. The ocean then absorbs more heat causing more ice to melt. Thawing permafrost follows a similar story. As it thaws, it releases more carbon, further warming the atmosphere and causing more permafrost to thaw.
“Right now, we’re mostly focused on how much carbon is entering the atmosphere as we burn fossil fuels to power our lives,” Waldrop said. “But, in the future, a lot of the carbon could come from non-human sources like permafrost thaw.”
This potential carbon source is a big deal, because for most of human history, permafrost has captured and stored carbon as frozen plant and animal remains, and the amount of stored carbon has been higher than that lost to the atmosphere through decomposition. However, as the planet warms, this trend could reverse.
“There are efforts to use soils and forests to store carbon, but permafrost is working in the opposite direction,” Waldrop said. “Land managers want to know how to keep carbon in the ground rather than see it released into the atmosphere.”
Permafrost secrets revealed
To understand how thawing permafrost could affect the global carbon cycle, which tracks carbon as it moves between the atmosphere (usually as carbon dioxide) and Earth (trapped in rocks, soils, and the ocean), Jones and her colleagues study both intact permafrost in forests and thawed permafrost from peatlands.
Working as a team, they bring back to the lab a core of permafrost, which they extract from the ground with special equipment. Then, they divide the core into different sections based on age. "We want to know how much carbon is in a meter of the core and how quickly it accumulated,” Jones said.
In one study, the team used a mass balance model and found that permafrost thaw turned peatlands into net carbon sources for decades following thaw. The peatlands eventually returned to being net carbon sinks on timescales of multiple centuries to millennia.
In another study, Jones, Waldrop, and Kristen Manies, an ecologist with USGS, studied permafrost in the Bonanza Creek Experimental Forest in Fairbanks, Alaska, and found that when permafrost formed after peat had accumulated, there was a smaller carbon loss than when permafrost and peat formed at the same time.
“Understanding what happened at the site will help to more accurately predict how much carbon is lost under future climate change scenarios when permafrost thaws,” Jones said.
Researchers are also looking into impacts from abrupt permafrost thaw, which can happen when warm surface conditions meet permafrost with a high content of ice. Although abrupt thaw covers a much smaller area than gradual thaw, it thaws a higher volume of ground at once, making its stored carbon likely to decompose and escape to the atmosphere.
One study found that carbon released from a specific area with abrupt permafrost thaw (~2.5 million square kilometers) could provide a similar climate feedback as gradually thawing permafrost from an area that’s 18 million square kilometers. “We are seeing more frequent instances of abrupt thaw now and expect to see that trend continue in the future,” Jones said.
In addition to examining the landscape, researchers are also studying what’s happening on a molecular level. For example. Waldrop and others are also looking at DNA stored in permafrost soil. “We can use microbes to see what kind of plant communities existed in Alaska over tens of thousands of years,” Waldrop said.
There’s also evidence that there are microbes active within the frozen permafrost. “There’s still a lot of liquid water in frozen soils, especially as it warms right before thaw” Waldrop said. These microbes are chewing up the carbon-rich organic matter found within the permafrost soils and releasing carbon to the atmosphere, sometimes in the form of methane.
“The discovery that microbes are active in frozen soils is important because it means that they have been able to transform the chemistry of carbon within the permafrost, which in turn can affect how fast carbon is released to the atmosphere once it thaws,” Waldrop said.
Waldrop studied when microbe activity and subsequent methane emissions would be highest during permafrost thaw, finding that the highest rates happened soon after thaw and declined over decades.
Permafrost thaw will force more carbon into the atmosphere. Eventually, that carbon will be recaptured and potentially frozen, if the conditions are right, but that reversal will take centuries to millennia. “The timescale does not align with what is necessary for climate mitigation,” Jones said. That means for the immediate future, permafrost thaw will be more of a carbon source than sink.
Working across agencies on a common goal
USGS scientists continue to closely work with experts from 15 other federal agencies as members of the Interagency Arctic Research Policy Committee to enhance both the scientific monitoring of and research on local, regional, and global environmental issues in the Arctic.
As part of the 2022-2026 plan, the USGS was tasked to advance our understanding of processes controlling permafrost dynamics and their impacts on ecosystems, infrastructure, and climate feedbacks, among other topics. “Arctic communities are feeling the effects of multiple challenges,” the plan states. It emphasizes unprecedented warming from climate change and thawing permafrost.
“Alaska is filled with amazing, wide-open spaces,” Waldrop said. “But if permafrost continues to thaw on an accelerated timeline, those spaces could dramatically change.”