Exclusive: Some Arctic Ground No Longer Freezing—Even in Winter

New data from two Arctic sites suggest some surface layers are no longer freezing.  If that continues, greenhouse gases from permafrost could accelerate climate change.

Nikita Zimov was teaching students to do ecological fieldwork in northern Siberia when he stumbled on a disturbing clue that the frozen land might be thawing far faster than expected.

Zimov, like his father, Sergey Zimov, has spent years running a research station that tracks climate change in the rapidly warming Russian Far East.  So when students probed the ground and took soil samples amid the mossy hummocks and larch forests near his home, 200 miles north of the Arctic Circle, Nikita Zimov suspected something wasn't right.

In April he sent a team of workers out with heavy drills to be sure.  They bored into the soil a few feet down and found thick, slushy mud. Zimov said that was impossible.  Cherskiy, his community of  3,000 along the Kolyma River, is one of the coldest spots on Earth.  Even in late spring, ground below the surface should be frozen solid.

Except this year, it wasn't.

Every winter across the Arctic, the top few inches or feet of soil and rich plant matter freezes up before thawing again in summer.  Beneath this active layer of ground extending hundreds of feet deeper sits continuously frozen earth called permafrost, which, in places, has stayed frozen for millennia.

But in a region where temperatures can dip to 40 degrees below zero Fahrenheit, the Zimovs say unusually high snowfall this year worked like a blanket, trapping excess heat in the ground.  They found sections 30 inches deep—soils that typically freeze before Christmas—that had stayed damp and mushy all winter.  For the first time in memory, ground that insulates deep Arctic permafrost simply did not freeze in winter.

"This really is astounding," says Max Holmes, an Arctic scientist with Woods Hole Research Center in Massachusetts.

The discovery has not been peer-reviewed or published and represents limited data from one spot in one year.  But with measurements from another scientist nearby and one an ocean away appearing to support the Zimovs' findings, some Arctic experts are weighing a troubling question:  Could a thaw of permafrost begin decades sooner than many people expect in some of the Arctic's coldest, most carbon-rich regions, releasing trapped greenhouse gases that could accelerate human-caused climate change?

Already, three of the last four years have been earth's hottest on record, with 2018 on schedule to be number four.  And the poles are actually warming far faster, with areas 300 miles north of the Arctic Circle in Norway reaching 90 degrees Fahrenheit this July.  If significant quantities of permafrost start thawing early, that would only make things worse.

"This is a big deal," says Ted Schuur, a permafrost expert at Northern Arizona University.  "In the permafrost world, this is a significant milestone in a disturbing trend—like carbon in the atmosphere reaching 400 parts per million."

Crossing a Threshold
Nearly a quarter of the Northern Hemisphere's landmass sits above permafrost.  Trapped in this frozen soil and vegetation is more than twice the carbon found in the atmosphere.

As fossil-fuel burning warms the Earth, this ground is thawing, allowing microbes to consume buried organic matter and release carbon dioxide and shorter-lived methane, which is 25 times as potent a greenhouse gas as CO2.

Permafrost temperatures across the Arctic have been rising since at least the 1970s—so much that small-scale localized thawing is already underway in many places.  But the vast majority of this frozen land is still insulated by an active layer of freezing and thawing ground above it.

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