SOURCE: National Geographic
DATE: August 20, 2018
SNIP: 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.
Nikita Zimov, like his father, Sergey Zimov, has spent years running a research station that tracks climate change in the rapidly warming Russian Far East. [I]n 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.
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.
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.
Now signs are emerging that the annual freeze-up can quickly change.
If a region’s active layer stops freezing consistently, consequences can be swift. Once unfrozen, soil microbes in the active layer can decompose organic material and release greenhouse gases year-round—not just in summer. And it exposes permafrost below to more heat so that layer, too, can begin thawing and releasing gases.
In ice-rich soils, such as in Siberia, the ground may slump. That can buckle roads and buildings and cause ice cellars to collapse. Such depressions also alter the landscape by forming troughs and bowls where snow can accumulate, making the ground even warmer in winter. Those troughs can fill with rain and snowmelt, forming new wetlands and tundra lakes, both of which expel large amounts of methane.
And the movement of all this water, above and below ground, can transport large amounts of heat, hastening thawing. Permafrost collapse can begin feeding on itself, releasing more greenhouse gases, which fuel more warming.
“When we simulate these things there are a number of processes the models don’t include—processes that multiply the transfer of heat,” says Daniel Fortier, an associate professor of geography with the University of Montreal. “I think it’s safe to say that things are happening faster than we were expecting.“