(Montreal) Another ecological disaster awaits the Arctic on the fringes of global warming.

While experts have long pointed to the threat posed by the release of massive amounts of greenhouse gases — methane and CO2 — that will escape as permafrost thaws, a new study shows that toxic contaminants of all kinds, accumulated for decades on industrial sites in the Far North, are also at risk of escaping.

The Nature Communications study, carried out by researchers at the Alfred-Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, identifies tens of thousands of contaminated industrial sites, including around 3,600 in the regions of permafrost of Canada and Alaska.

These are oil exploration or drilling sites, mining sites and former military installations, all places where toxic waste has been buried and stored over the decades under the premise that permafrost, presumably permanently frozen, represented a safe and impenetrable barrier. However, the melting of permafrost, whose name literally means “permanently frozen ground”, poses a threat that was not foreseen at the time.

“I’m not at all surprised to hear that these brownfields are going to degrade due to melting permafrost,” says Christopher Burn, an expert in permafrost, climate change and land ice at the Department of Geography of the Carleton University, Ottawa.

“What surprises me most is the mapping, which shows the extent of contaminated sites in the Arctic.

“When you look at the map, you see a lot of sites where you would expect, but there are also other dots all over the place indicating that there has been military or industrial or mining activity. When we look at the Canadian permafrost region, which occupies all of Canada’s North, we must recognize that there are very few places where there are no contaminated sites at the scale of this map. It’s everywhere,” Dr. Burn blurts out.

Tabatha Raman, a doctoral student in geography at Laval University who specializes in permafrost geomorphology, explains what is on the horizon for a thaw, as Canadian permafrost is composed not only of earth and rock, but also of many of ice.

“Water is an amazing transportation medium. Microplastics can be found all the way to the North Pole, thousands and thousands of miles from the sources of the plastic. In regions where there is contamination and where the permafrost is thawing, the ecosystem is certainly at risk. »

Moreover, says Christopher Burn, the time factor adds to this reality.

“The majority of these sites are near rivers and the ocean. With these kinds of contaminants, any area that is close to the source of contamination will not only end up with a high concentration, but also a persistent one. We are not talking here about a year or a season of contamination. Once these contaminants enter the aquifer system, they are there for a very long time. And since water carries everything over great distances, the problem will spread,” he warns.

So ultimately there are only two options: make amends or live with the mistakes of a past when environmental concerns were virtually non-existent, Professor Burn reminds us. “In the 1960s and 1970s when many of these now contaminated sites were created, the consensus was that the permafrost would be permanently frozen, hence the name. It was not even envisioned that we would have the kind of climate change that we now see in the northern regions. »

Money was a driving factor behind those decisions, he adds. “It’s much cheaper to bury everything in place than to take it out and that was the general practice in the 60s and 70s. But those companies had government permits at the time,” so it’s hard , legally, to make them bear the responsibility retroactively.

Daniel Fortier, professor of geography at the University of Montreal and director of the Geocryolab, a laboratory for the study of geomorphology and geotechnics of cold regions, notes that the age of several sites complicates the situation.

“We have mine tailings, for example what we call ‘sumps’. It is drilling muds and fluids that are inside the permafrost in the Northwest Territories, which will definitely cause the problem. We also have, of course, all the arctic villages that are powered by diesel generators, so we have several places where we store both diesel, kerosene, gasoline and various other products of that kind.” , explains Professor Fortier.

On the military side, we speak in particular of the former sites of radar installations of the DEW line (Distant Early Warning, the line of radars intended to quickly warn of missile attacks from Russia), but there is hope of this side, points out Christopher Burn. “Many of the DEW sites have been abandoned, but there has been some cleanup. Except that it turned out to be very expensive because on many of these sites, we had buried a lot of PCBs and other contaminants that cannot stay buried. Obviously, if these materials are released into the environment with the melting of the permafrost, it will be a serious problem. The DEW Line cleanup is a very expensive program, but it is still ongoing. »

The worst contaminated sites come from the mining sector and are located in the Northwest, points out Mr. Burn, who puts the Cyprus Anvil lead and zinc mine in Faro, Yukon, at the top of the list. “The company left in 1998 without ever getting closure approval or providing a restoration plan,” he laments.

The other case he points to is almost surreal, says the researcher, when it was decided to refreeze the thawed permafrost at the Giant gold mine in Yellowknife, in the Northwest Territories. “They decided the problem is perpetual because they buried arsenic trioxide in the form of dust and they want it to be frozen and stay frozen. So they decided to install a power plant on site to keep the ground frozen. It is extremely expensive. But it would be even more expensive and dangerous to take it out and transport it to the South for treatment. »

Quebec is doing pretty well, says Daniel Fortier. “We have less in Quebec than in northwestern Canada,” he describes. On the one hand, there has been no significant oil exploration and drilling activity and the mining industry is recent enough to have been subject to stricter standards than 50 or 60 years ago. “What is currently happening at the mining level in Quebec is well monitored and it has been well established. »

Christopher Burn, confirms. “In Quebec, there are fewer problems. The Raglan mine, for example, is in operation now. There will certainly be long-term problems, as with any northern mining activity, but there are now provisions under which companies must post a bond allowing those who will inherit the site-normally the government-to have the funding required to secure the site. »

On the other hand, Northern Quebec will not escape a possible dispersion of contaminants that will leak into water bodies with the thawing of the permafrost. That thaw, warns Christopher Burn, will come sooner rather than later. “On the one hand, we did not think that greenhouse gas emissions into the atmosphere could have such a massive impact on the climate, as we must have seen over the past 50 years. On the other hand, we did not understand to what extent climate change would be amplified in the polar regions. We are seeing this amplification now, but it took 50 years of data to convince us that what we are seeing is real, rather than just a variation in climate associated with background fluctuations. »