Permafrost is thawing so quickly in the Arctic it's leaving sinkholes
Rapidly thawing permafrost in the Arctic has scientists worried. According to a new study published Monday in the journal Nature Geoscience, the ice that holds the soil together is melting, causing hillsides to collapse and massive sinkholes to open up as a result. And that dramatic disruption to the landscape is only part of the story — a bigger concern is the growing amount of carbon this process releases into the atmosphere.
The rapid melting of previously solid permafrost promotes microbial activity, which releases greenhouse gases like CO2 and methane into the atmosphere, causing carbon levels to rise. Higher carbon levels, in turn, contribute to global warming. The study warns that the level of emissions from the Arctic could be much higher than previously estimated.
Merritt Turetsky, lead author of the study, said the abrupt thawing is "fast and dramatic" and "affects landscapes in unprecedented ways."
"Abrupt thawing of permafrost will double previous estimates of potential carbon emissions from permafrost thaw in the Arctic," Turetsky said in a press release.
"Forests can become lakes in the course of a month, landslides occur with no warning, and invisible methane seep holes pose threats to the safety of hunters and snowmobilers traveling across the land."
The new study distinguishes between gradual permafrost thaw, which affects permafrost and its carbon stores slowly, versus more abrupt types of permafrost thaw.
Less than 20% of northern permafrost is susceptible to this kind of rapid thaw, which occurs where permafrost contains high levels of ice in the ground. Permafrost that abruptly thaws is what scientists are worried about because it is a large emitter of carbon, including the release of carbon dioxide and methane, which is an even more potent greenhouse gas.
The researchers say that even though at any given time less than 5% of the Arctic permafrost region is likely to be experiencing abrupt thaw, their emissions will equal those of areas experiencing gradual thaw.
"Where permafrost tends to be frozen lake sediment or organic soils, the type of earth material that can hold a lot of water, these are like sponges on the landscape," Turetsky said. "When you have thaw, we see really dynamic and rapid changes."
When ice-rich permafrost thaws, it leads to a phenomenon known as thermokarst, which results in the land surface being ravaged. This process happens naturally in some places, but it is accelerating with global warming and rapid thaw. Thermokarst depressions or landslides can now develop very quickly, in the matter of days to weeks, leading to extreme consequences for the landscape and the atmosphere.
"Abrupt permafrost thaw can occur in a variety of ways, but it always represents a dramatic abrupt ecological shift," Turetsky said. "Systems that you could walk on with regular hiking boots and that were dry enough to support tree growth when frozen can thaw, and now all of a sudden these ecosystems turn into a soupy mess."
The Arctic is warming at more than two times the pace of the world as a whole.
The latest findings bring new urgency to including permafrost in all types of climate models, along with implementing strong climate policy and mitigation, Turetsky said.
"We can definitely stave off the worst consequences of climate change if we act in the next decade," said Turetsky. "We have clear evidence that policy is going to help the north and thus it's going to help dictate our future climate."