Looking for one more reason to worry about climate change? No? Well, here’s one anyway. Rising global temperatures are causing parts of the Siberian tundra to spontaneously explode.
Scientists have been studying this bizarre phenomenon since 2014, when a mysterious 165-foot-deep (50-meter-deep) hole suddenly appeared on the Yamal Peninsula in northwest Siberia. Since then, they’ve identified more than a dozen similar craters on the Yamal and Gyda peninsulas and linked their formation to climate change, but key questions remain. Now, a new study could offer some long-awaited answers.
The mystery of Siberia’s sudden holes
Research published Monday in the journal Science of the Total Environment builds on previous work that found that the region’s unique geology—coupled with rising temperatures—can trigger sudden eruptions of methane gas from beneath the permafrost. As the permafrost thaws, water seeps down into subsurface pockets of saltwater called cryopegs, kicking off this process.
In the Yamal Peninsula, cryopegs are about 3 feet (1 meter) thick and sit up to 165 feet (50 meters) underground. Below them lies another layer filled with crystallized methane. As meltwater seeps into the cryopegs, pressure builds, creating cracks in the soil that travel up toward the surface. This reverses the pressure gradient, causing a sudden drop in pressure at depth that damages the methane crystals and—BOOM!—triggers an explosive release of methane gas.
Sounds plausible, right? But the findings didn’t explain why the explosions only occur in Siberia, even though the rest of the Arctic is rapidly warming too. In fact, none of the existing models for the craters could answer this question, Helge Hellevang—an environmental geoscientist at the University of Oslo and lead author of the new study—told the New York Times.
Cracking the case: Why Siberia?
To get to the bottom of this, he and his colleagues critically reviewed those existing models. The team concluded that the craters are too large to be explained by ruptures of small gas pockets alone. They constructed their own computer models to gain a more nuanced understanding of their formation, finding that it may be related to faulting in the area.
Gas and heat rising up through the faults from deep underground can become trapped in a sealed cavity beneath the permafrost, their models suggest. As the permafrost melts, that seal weakens. Meanwhile, pressure builds inside the cavity as higher temperatures release gas trapped under the ice. This, combined with highly pressurized gas rising from faults deep below, can make the whole system go kablooey.
Thus, deep heat and gas rising from beneath the permafrost are likely the main cause of these craters, according to Hellevang and his colleagues. Atmospheric heating still plays a role, albeit indirectly. Warming speeds up thawing, weakening the permafrost and helping new lakes and rivers form. This sets the stage for gas and heat to travel through the faults and trigger explosions.
“As atmospheric heating and weakening of the surface permafrost [continue], it is likely that more explosions will occur,” Hellevang told the NYT. He said he would like to observe how these gas craters transform into lakes over time to see if they come to resemble other lakes in the region. This could help explain the origin of some of the many round lakes that dapple Siberia’s landscape.