Climate change: thawing permafrost a triple-threat

Thawing Arctic permafrost laden with billions of tonnes of greenhouse gases not only threatens the region’s critical infrastructure but life across the planet, according a comprehensive scientific review.

Nearly 70 percent of the roads, pipelines, cities and industry -- mostly in Russia -- built on the region’s softening ground are highly vulnerable to acute damage by mid-century, according to one of half-a-dozen studies on permafrost published this week by Nature.

Another study warns that methane and CO2 escaping from long-frozen soil could accelerate warming and overwhelm global efforts to cap the rise in Earth’s temperature at livable levels. Exposure of highly combustible organic matter no longer locked away by ice is also fuelling unprecedented wildfires, making permafrost a triple threat, the studies report.

Blanketing a quarter of the northern hemisphere’s land mass, permafrost contains twice the carbon currently in the atmosphere, and triple the amount emitted by human activity since 1850.

By definition, it is ground that has been at temperatures colder than zero degrees Celsius (32F) for more than two years, though much permafrost is thousands of years old.

Temperatures in the Arctic region have risen two to three times more quickly over the last half-century than for the world as a whole -- two to three degrees Celsius above pre-industrial levels. The region has also seen a series of freakish weather anomalies, with temperatures in winter flaring up to 40C above previous averages.

Permafrost itself has, on average, warmed nearly 0.4C from 2007 to 2016, "raising concerns about the rapid rate of thaw and potential old carbon release," note researchers led by Kimberley Miner, a scientist at the California Institute of Technology’s Jet Propulsion Laboratory.

Their study projects a loss of some four million square kilometres of permafrost by 2100 even under a scenario in which greenhouse gas emissions are significantly reduced in the coming decades.

Rising temperatures are not the only driver of accelerated melting.

Arctic wildfires rapidly expand the layer of permafrost subject to thawing, the researchers point out. As the climate warms, these remote, uncontrolled blazes are projected to increase 130% to 350% by mid-century, releasing more and more permafrost carbon.

Indeed, thawing renders buried organic carbon more flammable, giving rise to "zombie fires" that smoulder throughout frigid winters before igniting again in Spring and Summer. "These below-ground fires could release legacy carbon from environments previously thought to be fire-resistant," Miner and colleagues warn. The most immediate threat is to the region’s infrastructure.

Northern hemisphere permafrost supports some 120,000 buildings, 40,000 kilometres (25,000 miles) of roads and 9,500 kilometres of pipelines, according to another study led by Jan Hjort, a scientist at Finland’s University of Oulu.