To build a home in Inuvik in the 1950s, construction workers had to drive wooden piles about seven metres deep into the permafrost to account for naturally shifting land.

Today, homebuilders in the Northwest Territories town must hammer those piles nearly 20 metres into the ever-softening Arctic ground.

“It’s probably the most telling tale of what’s happening,” said Mayor Denny Rodgers. “There are areas in town . . . that are being washed away.”

As the world continues to warm, so too does the northern hemisphere’s permafrost — located mostly in Canada, Alaska, Russia and parts of Scandinavia. By the middle of the century, an estimated 20 per cent of permafrost in the north is likely to disappear, a 2007 International Council on Climate Change report says.

Beyond Inuvik and other northern communities, where the continued thaw poses a significant environmental threat, the impact of melting permafrost is predicted to be widespread.

Scientists with the Permafrost Carbon Network warned in a Nature article released Thursday that melting permafrost, loaded with enormous amounts of toxic gasses, is a ticking time bomb that could intensify global warming.

The group of scientists predicts that about 45 billion metric tonnes of greenhouse gasses trapped in frozen ground will slowly leech into the air by 2040 as permafrost continues to melt.

By 2100, an estimated 300 billion tonnes of carbon from carbon dioxide and methane are expected to disperse into the atmosphere.

The pollution from permafrost carbon will never outpace factories, cars and other human fossil fuels, said Edward Schuur, a University of Florida scientist and lead author of the study in Nature. But it will accelerate the pace of global warming, he said.

“Unmanaged parts of the earth, arctic systems, are going to have a major role in the pace of climate change in the future,” he said.

Carbon, naturally accumulated in the soil as plants and animals decay, has been locked in the frozen ground for thousands of years. The trouble comes when soil begins to thaw. As it unfreezes, bacteria attack the carbon and release carbon dioxide and methane into the air.

While previous permafrost studies tested the top metre of soil that thawed in summer months, scientists say carbon found several metres below the surface now pose a threat due to rising temperatures.

That carbon will reach the surface as soil thaws in the summer months and transform into toxic gasses over the next few decades if global warming continues on par, the study said.

Little is known about how quickly carbon will be emitted from permafrost when it melts and how it will affect the atmosphere.

But the physical changes already seen in northern landscape is telling, said Dr. Merritt Turetsky, a University of Guelph ecologist who participated in the permafrost study.

“The (International Panel on Climate Change) outlined several scenarios and we are exceeding the worst case scenario,” she said.

Turetsky began her research on Canadian permafrost in the late 1990s. Over the last decade, she travelled to a number of permafrost sites in northern Alberta and the Northwest Territories — and she’s seen the melting permafrost drastically change the landscape.

“In that short time, the transformations are quite drastic,” she said. “It literally turns a forest into a semi-aquatic pool . . . vegetation starts to slump, thaw and sink into the ground. Trees start to pitch. This is causing the landscape to change in ways that most of the community hasn’t quite recognized yet.”

She said “collapse scars,” where trees and other types of vegetation slump over and sink into ponds, are becoming an increasingly common sight across the Canadian North.

In Inuvik, Rodgers said the town has experienced “permafrost stumpage” over the last several years — eroding roadsides and ditches dug in the permafrost that quickly transform into large, gaping holes.

Turetsky said the risks posed by permafrost remain high if human-made greenhouse gases remain on pace.

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With nearly half of the country covered by permafrost, the impact will reach beyond already affected northern communities in the coming decades if scientists’ predictions are accurate.

Turetsky said a limit on human-made emissions could help keep some carbon frozen in the permafrost, but added that she fears an enormous amount of damage has already been done.

“The analogy is that it’s a big train about to derail,” she said. “Once it begins, permafrost thaw occurs slowly but you can’t stop it. That lack of control makes anybody feel nervous.”

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