Scientists might have to change their projected timelines for when Greenland’s permafrost will completely melt due to man-made climate change, now that new research from Denmark has shown it could be thawing faster than expected.
Published Monday in the journal Nature Climate Change, the research shows that tiny microbes trapped in Greenland’s permafrost are becoming active as the climate warms and the permafrost begins to thaw. As those microbes become active, they are feeding on previously-frozen organic matter, producing heat, and threatening to thaw the permafrost even further.
In other words, according to the research, permafrost thaw could be accelerating permafrost thaw to a “potentially critical” level.
“The accompanying heat production from microbial metabolism of organic material has been recognized as a potential positive-feedback mechanism that would enhance permafrost thawing and the release of carbon,” the study, conducted by researchers at the University of Copenhagen’s Center for Permafrost, said. “This internal heat production is poorly understood, however, and the strength of this effect remains unclear.”
The big worry climate scientists have about thawing permafrost is that the frozen soil is chock-full of carbon. That carbon is supposed to be strongly trapped inside the soil, precisely because it’s supposed to be permanently frozen — hence, “permafrost.”
However, as temperatures in the Arctic have risen due to human-caused climate change, permafrost is thawing, and therefore releasing some of that trapped carbon into the atmosphere. It’s yet another feedback loop manifesting itself in Arctic permafrost regions — as climate change causes it to thaw, the thawing causes more climate change, which causes more thawing, et cetera, et cetera.
What makes this new research so important is that it adds to the urgency of stemming permafrost thaw. Because even without this new discovery of heat-producing microbes, estimates for carbon releases from thawing permafrost have been alarmingly large. According to the National Snow & Ice Data Center, there are about 1,700 gigatons of carbon currently frozen in permafrost — more than the total amount in the atmosphere now (Earth’s atmosphere contains about 850 gigatons of carbon, according to the Center).
Without considering microbes, the average estimate is that 120 gigatons of carbon will be released from thawing permafrost by 2100, which would raise the average global temperature 0.29 degrees. After 2100, if climate change worsens, total permafrost emissions roughly double. That’s confirmed by National Snow and Ice Data Center research scientist Kevin Schaefer’s research, which took the average of 15 peer-reviewed estimates of future carbon releases from thawing permafrost.
Schaefer, who was also one of the reviewers of the microbe study, told ThinkProgress that this is particularly alarming because emissions from permafrost are “completely irreversible.”
“These are permanent emissions,” he said. “Once you thaw out that material, there’s no way to put that organic matter back into the permafrost … you can’t re-freeze the permafrost.”
It’s also unclear whether the carbon that gets released once permafrost thaws will manifest itself as carbon dioxide or methane, which has a much greater impact on climate change — specifically, for each pound emitted compared with carbon dioxide, methane has a 20 times greater impact on atmospheric warming over a 100-year period, according to the Environmental Protection Agency. The New Scientist reports that if the Arctic gets warmer and drier, the microbes trapped within the permafrost can be expected to produce carbon dioxide. But if the environment gets warmer and wetter, the microbes that thrive will tend to produce methane.
The discovery of heat-producing microbes only threatens to add more uncertainty to permafrost emissions projections. Because even though we do know they can accelerate thaw, we don’t know how much.
“One of the biggest uncertainties is how much heat do the microbes generate as they eat the organic material,” Schaefer said. “It will accelerate thaw, but the question is how much. I don’t think that has been answered yet.”
So, that’s a lot of bad news when it comes to global climate change. But the good news, Schaefer said, is that accelerated thawing of Arctic permafrost can be prevented if warming is limited to a global average of 2 degrees Celsius. That 2 degree limit is, incidentally, the objective of international climate negotiations scheduled to take place at the end of this year.
“If we limit the warming to 2 degrees, it will also limit the emissions from thawing permafrost,” Schaefer said. “But the more we dump into the atmosphere, the greater the emissions from permafrost will be.”