HUMANS HAVE LONG sullied the Arctic with industrial development—mining operations, oil and gas exploration, military bases. That’s contaminated the landscape with a bevy of toxicants, including radiological material, heavy metals, insecticides, and fuels. That nastiness was often intentionally buried in frozen ground known as permafrost. In theory, as long as that ground remained frozen, the pollutants would stay locked away.

No longer. An alarming new paper in the journal Nature Communications estimates that between 13,000 and 20,000 contaminated sites are splayed across Arctic permafrost regions, with 3,500 to 5,200 in areas that’ll be affected by thawing soils before the end of the century. The region is already warming rapidly, more than four times faster than the rest of the planet. And that estimated number of sites is likely low, the scientists warn, because thaw might dramatically accelerate in some places. 

As permafrost degrades, it collapses, releasing buried contaminants that flow out in the melted ice. The ground sinks—often spectacularly and rapidly—dragging down aboveground infrastructure like fuel tanks and pipelines. Indeed, that was the suspected cause of a 2020 environmental disaster in Norilsk, Russia, in which 17,000 tons of oil leaked from a collapsed tank.

“The assumption is that permafrost is a hydrological barrier, and it will remain there forever,” says permafrost researcher Moritz Langer, of the Alfred Wegener Institute and Vrije Universiteit Amsterdam, lead author of the new paper. “That was the assumption for all of these very old sites—especially from the ‘70s, ‘80s, up until the ‘90s—when climate warming and the problem of permafrost thaw was not really on the radar of most people.”

Langer and his colleagues found that 70 percent of these sites are in Russia, with others across Alaska, Canada, and Greenland. Some facilities are abandoned and difficult to access and clean up. Others are still operational, and producing yet more toxicants to leak into the environment. (The new paper doesn’t distinguish, though, exactly which sites are which.) As the Arctic warms, expect industrial and military development to creep farther north, adding more contaminants while putting more people in contact with them. And the mushier the soil gets, the harder it will be to use heavy equipment to clean up the messes.

“This idea that somehow we have, functionally, a number of potential Superfund sites that were completely unknown until this paper, but could be mobilizing into the Arctic and potentially international environment, is pretty terrifying,” says Kimberley R. Miner, a climate scientist who studies permafrost contamination at NASA’s Jet Propulsion Laboratory but wasn’t involved in the new paper. “To see them take that idea and apply it to actual maps and get actual sites, with permafrost disturbance underneath, was so mind-blowing to me.”

Existing sites are already plagued by a slew of environmental troubles. Oil leaks come from both wells and from pipelines. Radioactive material is buried around military bases. Pesticides like DDT are packed in barrels, then buried. Mining operations are notorious for emitting heavy metals like mercury; other sites are full of arsenic, lead, and other highly toxic elements and compounds. Trucks and heavy machinery carry liquid fuels like diesel, which are prone to spill. 

Once the ground is no longer frozen enough to form a barrier, those contaminants will seep into rivers and ponds, corrupting highly sensitive ecosystems. “This, we think, could also be a dangerous situation for people living up in the high north,” says Langer, as the contaminants mix with drinking water.

That water will eventually empty into the ocean and ride elsewhere on currents. Toxicants can also get airborne: Indeed, the Arctic is already dusted with lead from burning leaded gasoline. Mercury, too, could escape mining operations by taking to water and air. “Mercury that came from the burning of coal and fossil fuels from a century or two centuries ago is still cycling through our biosphere,” says Kevin Schaefer, a climate scientist at the University of Colorado, Boulder, who studies permafrost contaminants but wasn’t involved in the new paper.

Human activity in the Arctic only exacerbates the thaw. Dark-colored roads absorb the sun’s energy, heating the soil. Digging up dirt and tossing it on top of snow darkens the whiteness that would normally bounce light off the landscape. Vehicle tires chew up the soil. “You already have rapidly changing environmental conditions,” says George Washington University climate scientist Dmitry Streletskiy, who studies permafrost but wasn’t involved in the new paper. “But then, of course, on top of those rapid changes, you have concentrated human presence—you have industry and infrastructure. So those are really focal points, where you in many ways amplify those changes associated with climate.”

Oh, and the giant new Willow drilling project in Alaska that the Biden administration just approved? That’ll be on permafrost too. “Think about what it takes to establish a pipeline,” says Miner. “You’re going to need a road. You’re going to have people walking in and out, trampling the permafrost. All of that is going to lead to increased thaw and increased potential for contamination and disturbances to the very fragile tundra landscape. So it’s just impacts upon impacts upon impacts.”

This new paper only considered gradual permafrost thaw. But permafrost can collapse much more rapidly, digging holes known as thermokarst. As ice becomes liquid water, it loses volume, forming a crater in which microbes produce the highly potent greenhouse gas methane. This further warms the atmosphere and accelerates permafrost thaw—a gnarly climatic feedback loop.

Adding yet more peril is that as the Arctic warms, wildfires are proliferating. If one sweeps through a contaminated site, it’ll send up plumes of toxicant-laden smoke. That will in turn exacerbate the thaw: Scientists have previously calculated that in north Alaska, thermokarst formation has accelerated by 60 percent since 1950, thanks to wildfires.

In other words, Langer says, their paper’s projection is “pretty conservative.” Some of the sites might thaw even earlier.

Permafrost is already deforming communities in the far north. Airport runways are sinking, roads are wrinkling, and buildings are crumbling. “It’s no longer some ambiguous thing that might happen in the future—it’s happening today, even as we speak,” says Schaefer. “If this infrastructure becomes damaged because of thawing permafrost, it’s extremely expensive and extremely difficult to resolve. These areas are very remote. You can only do things in certain times of the year, mainly the summer.” 

If thermokarst opens a hole in your runway, for instance, it might cut off surrounding communities that rely on supplies brought in by plane. And if you can’t fly, you can’t get out of many places around the Arctic. “It’s not like the Lower 48—if I don’t make it to Denver, I’ll fly to Colorado Springs,” says Schaefer. “These are all really key infrastructure, and it’s really difficult to build and maintain.”

But this new paper is at least a step toward localizing the problem, directing governments to where cleanup might be required. Early scientific sleuthing like this is a start, but a fix will take putting a lot of boots on increasingly soggy ground. “In order to manage something, you have to measure it,” says Miner. The next step would take a massive push—one like the US Environmental Protection Agency began in the 1980s to clean up Superfund sites. But with such a patchwork of nations and corporations responsible for the mess, it’s not clear when—or if—that work would start.