14 august 2019

Arctic permafrost is thawing fast. That affects us all.

As the frozen ground warms much faster than expected, it’s reshaping the landscape—and releasing carbon gases that fuel global warming

By Craig Welch, National Geographic, August 14. 2019

Sergey Zimov, an ecologist by training, tossed a woolly mammoth bone on the pile. He was squatting in mud along the cool, wide Kolyma River, below a towering cliff of crumbling earth. It was summer in eastern Siberia, far above the Arctic Circle, in that part of Russia that’s closer to Alaska than to Moscow. There wasn’t a speck of frost or snow in sight. Yet at this cliff, called Duvanny Yar, the Kolyma had chewed through and exposed what lies beneath: a layer of frozen ground, or permafrost, that is hundreds of feet deep—and warming fast.

Twigs, other plant matter, and Ice Age animal parts—bison jaws, horse femurs, mammoth bones—spilled onto a beach that sucked at Zimov’s boots. “I love Duvanny Yar,” he said as he yanked fossils from the muck. “It is like a book. Each page is a story about the history of nature.”

Across nine million square miles at the top of the planet, climate change is writing a new chapter. Arctic permafrost isn’t thawing gradually, as scientists once predicted. Geologically speaking, it’s thawing almost overnight. As soils like the ones at Duvanny Yar soften and slump, they’re releasing vestiges of ancient life—and masses of carbon—that have been locked in frozen dirt for millennia. Entering the atmosphere as methane or carbon dioxide, the carbon promises to accelerate climate change, even as humans struggle to curb our fossil fuel emissions.

Methane, a potent greenhouse gas, is bubbling from thawing ground under lakes across the Arctic. In winter, surface ice traps the gas. On this pond near Fairbanks, Alaska, scientists have drilled through the ice and set the escaping methane on fire.

Few understand this threat better than Zimov. From a ramshackle research station in the gold-mining outpost of Cherskiy, about three hours by speedboat from Duvanny Yar, he has spent decades unearthing the mysteries of a warming Arctic. Along the way, he has helped upend conventional wisdom—especially the notion that the far north, back in the Pleistocene ice ages, had been an unbroken desert of ice and thin soils dotted with sage.

Instead, the abundant fossils of mammoths and other large grazers at Duvanny Yar and other sites told Zimov that Siberia, Alaska, and western Canada had been fertile grasslands, rich with herbs and willows. As these plants and animals died, the cold slowed their decomposition. Over time, windblown silt buried them deep, locking them in permafrost. The upshot is that Arctic permafrost is much richer in carbon than scientists once thought.

Now new discoveries suggest that the carbon will escape faster as the planet warms. From the unexpected speed of Arctic warming and the troubling ways that meltwater moves through polar landscapes, researchers now suspect that for every one degree Celsius rise in Earth’s average temperature, permafrost may release the equivalent of four to six years’ worth of coal, oil, and natural gas emissions—double to triple what scientists thought a few years ago. Within a few decades, if we don’t curb fossil fuel use, permafrost could be as big a source of greenhouse gases as China, the world’s largest emitter, is today.

We aren’t accounting for that. The UN’s Intergovernmental Panel on Climate Change has only recently started incorporating permafrost into its projections. It still underestimates just how wide Pandora’s freezer could swing open—and how much havoc that could unleash.

Permafrost’s potential to warm the planet is dwarfed by our own. But if we hope to limit warming to two degrees Celsius, as 195 nations agreed to during the 2015 Paris talks, new research suggests we may have to cut emissions eight years sooner than IPCC models project, just to account for the thawing that will be going on.

It is perhaps our least appreciated reason to hasten a transition to cleaner energy: To reach whatever goal we set to combat warming, we’ll need to move even faster than we think.


>>> Back to list