Every winter across the Arctic, the top few inches or feet of soil and rich plant matter freezes up before thawing again in summer
A number of scientists have made the startling discovery that sections of arctic soil which normally freezes had stayed damp and mushy throughout the winter.
This top layer of soil insulates the arctic permafrost. If it does not freeze, then the permafrost itself could begin to thaw, releasing trapped greenhouse gases into the air.
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.
However, in April this year, Russian Scientist Nikita Zimov sent a team of workers with heavy drills, who found that the top layer of soil at Cherskiy, Russia had not frozen. Cherskiy is one of the coldest places on earth, and ground below the surface should be frozen solid even in late spring, according to National Geographic.
Nikita Zimov is the son of Sergey Zimov. The elder Zimov is one of the first scientists anywhere to show that Siberia contains enormous reserves of especially carbon-rich permafrost and is held in high regard by many researchers.
"He knows that landscape so well that he is very rarely wrong," said Katey Walter Anthony, an associate professor at the University of Alaska in Fairbanks, who studies methane in Arctic lakes. "For him to believe a process is important is valuable."
"This is a big deal," Ted Schuur, a permafrost expert at Northern Arizona University, told National Geographic. "In the permafrost world, this is a significant milestone in a disturbing trend—like carbon in the atmosphere reaching 400 parts per million."
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.
Eleven miles downriver from where the Zimovs’ started their drilling, Mathias Goeckede with Germany's Max Planck Institute for Biogeochemistry tracks carbon exchange between the earth and the atmosphere. Measurements at his site show that snow depth there has roughly doubled in five years.
When excessive snow smothers the ground, warmth below the surface may not dissipate during winter. Data from a drill hole on Goeckede's site show that temperatures 13 inches below ground rose by about 6 degrees Celsius.
"This is just one site, and it's just five years, so this really should be considered just a case-study," Goeckede said. "But if you assume it's a trend or that it might continue like this, then it's alarming."
Vladimir Romanovsky, permafrost expert at the University of Alaska in Fairbanks, said: "For all years before 2014, the complete freeze-up of the active layer would happen in mid-January. Since 2014, the freeze-up date has shifted to late February and even March."
If a region's active layer stops freezing consistently, soil microbes in the active layer can decompose organic material and release greenhouse gases all-year-round and not just in summer. Furthermore, it exposes permafrost below to more heat, and that layer can begin thawing and releasing gases and release gases as well.