What happens when the Arctic permafrost melts? - Brendan Rogers and Jessica Howard
In June 2022, a gold miner in the Canadian Yukon made a remarkable discovery. While working on the traditional lands of the Tr’ondëk Hwëch’in First Nation, he uncovered the exceptionally well-preserved frozen remains of a woolly mammoth calf that died 30,000 years ago. But this find isn’t the only of its kind because the Arctic holds many buried secrets.
About 15% of the Northern Hemisphere contains permafrost—that is, ground that doesn’t thaw seasonally, but has instead stayed frozen for at least two years—and, typically, much longer. The oldest permafrost yet discovered is located in the Yukon and has been frozen for 740,000 years. The thickness of permafrost also ranges, from just 1 meter in some areas to over a kilometer in others. And permafrost is exceptionally good at preserving biological remains.
If any ice crystals are close to remains buried in permafrost, they help draw moisture away. And microorganisms that would otherwise quickly decompose plant and animal tissues operate at slower metabolic rates in these subfreezing temperatures. The outcome is that, instead of having to rely on fossilized skeletons to extrapolate what an ancient animal might have looked like, permafrost can sometimes offer scientists literal freeze-frames of times long gone.
In 2016, another gold miner came face-to-face with a 7-week-old grey wolf pup that had been preserved in permafrost for 57,000 years. Researchers learned that she’d been feasting on salmon and think she died quickly, possibly when the den she was nestled in collapsed. In 2020, reindeer herders encountered remains that unmistakably belonged to a bear. But it turned out that they were as much as 39,500 years old. They belonged to a cave bear. Its species went extinct about 24,000 years ago.
Before this, scientists had only ever seen cave bear skeletal remains. Even incomplete animal remains found in permafrost have yielded incredible results. In 2021, researchers identified a new species of mammoth by reconstructing DNA sequences from 1.6-million-year-old mammoth teeth—making it the oldest sequenced DNA on record. And extraordinary finds go beyond the animal kingdom: in 2012, scientists successfully regenerated a flowering tundra plant from seeds they found encased in 32,000-year-old squirrel burrows.
However, all the prehistoric remains we have yet to discover in permafrost are at risk, along with much more, because permafrost is thawing rapidly. Climate change is warming the Arctic at 3 to 4 times the rate of the rest of the world. And an increased frequency in extreme weather events, like lightning and wildfires, is burning the plants and soil that otherwise help to keep permafrost cool.
When permafrost thaws, it has concerning and far-reaching effects. The ground can fracture and collapse in on itself, and the landscape can experience flooding and erosion, making previously stable trees tilt and form so-called “drunken forests.” It can also trigger massive landslides and threaten critical infrastructure. By the year 2050, permafrost thaw may endanger 3.6 million people. This includes many Indigenous and First Nations people who have lived across the Arctic region since time immemorial. Right now, they’re dealing with difficult decisions about how to protect their communities and traditional ways of life in the face of climate change.
The effects of thawing will also extend far beyond the Arctic. This is because permafrost stores an estimated 1.6 trillion tons of carbon. That’s over double the amount in Earth’s atmosphere as of 2022—and more than humans have ever released by burning fossil fuels. Permafrost is one of the world’s largest carbon reservoirs because of all the organic material it contains—some as intact remains, but much of it in the form of partially decomposed soils and sediments.
When it begins thawing, microorganisms decompose organic material more efficiently and release gases like carbon dioxide and methane. This triggers a feedback loop: as more gases are released, the climate warms, causing more permafrost to thaw and release even more greenhouse gases. To preserve snapshots of what the planet was like thousands of years ago—when mammoths and cave bears trod its terrain—and to support the diversity of life on Earth thousands of years to come, the Arctic needs to keep its cool.