Locked away in the Arctic permafrost is what's frequently called the "ticking time bomb" of climate change—methane, a greenhouse gas many times more powerful than carbon dioxide. There's widespread worry that, as the permafrost thaws, large amounts of methane will spew into the Earth's atmosphere, worsening the effects of climate change.
There's reason to be concerned. The Arctic is warming faster than anywhere else on Earth, and the permafrost—which acts like a cap over vast amounts of methane, preserved there for millions of years—is thawing. But scientists still don't know how much methane is leaking out and how quickly, or whether it could realistically reach a "tipping point." Understanding all this is crucial, and new research gets us closer.
Scientists have made a high-resolution map of methane emissions across the Mackenzie Delta region in Canada's Arctic. The area comprises "10,000 square kilometers," Katrin Kohnert of the GFZ German Research Centre for Geosciences told me. Until now, most of the research we had on methane leaking from the permafrost came from localized studies on the ground, explained GFZ scientist Torsten Sachs. Sachs and Kohnert are authors on the paper, published Wednesday in Scientific Reports, describing how their team used methane-sniffing airplanes to survey the region and get a sense of what was happening.
"This is the first study using this particular method with airplanes," Sachs told me. According to him, the plane is a modernized and modified DC-3, originally built in 1943.
Flying about 50 meters above ground over the Arctic between July 2012 and July 2013, the researchers had a bird's eye view.
"He's flying a pretty large airplane extremely close to the ground. It's pretty unique," Charles Koven, research scientist with the Earth and Environmental Sciences Area at the Lawrence Berkeley National Lab, told me in a phone call. Koven didn't participate in this paper, and hadn't had a chance to read it before I spoke with him, but he is familiar with Sachs' work. "Torsten has a tolerance for risk that's above that of most people," Koven added.
Permafrost is unequally thick across the Mackenzie Delta, Sachs and Kohnert explained in a phone call. In some places, it's relatively thin (about 100 meters) and in other places it's up to half a kilometre thick. Their team found that certain "hotspots" representing only 1 percent of the region—places where it was permeable, akin to cracks or holes in the cap—contributed 17 percent of the annual estimated methane emissions.
Methane is being released from the permafrost in a couple of different ways. As soil thaws, microbes munch away at its organic materials, producing greenhouse gases. Less well understood is the release of "geologic" methane contained in the massive oil and gas deposits across the Arctic, and the latter is what has many people concerned.
Thawing permafrost will contribute not only to increased "biogenic" methane (from microbes), but also "increased emissions of geologic [methane]," the paper reads, "currently still trapped under thick, continuous permafrost, as new emissions pathways open."
Does that mean we could reach a dramatic "tipping point" where the permafrost is so degraded that methane dumps rapidly into the atmosphere? Sachs compared it to punching holes in a jar's lid. "In theory, you could imagine [tapping] big reservoirs underneath," he said. "But usually the thawing is gradual. I don't think it will be catastrophic."
Koven said that scientists need more observations of what's going on at every scale—localized studies on the ground, alongside studies from airplanes and space-based satellites—to understand the risks. There are still so many unknowns.
"What we do know, with some confidence, is that warming is going to lead to a thawing of the permafrost, which will lead to a bunch of different outcomes," he said. One will be the release of more greenhouse gases, including methane. "Another thing we don't know nearly as well," Koven continued, is whether we could hit some kind of a tipping point. "The evidence for those is not as good, but we can't rule them out completely."
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