Some scientists suspect that permafrost acts as a cap that protects hydrates from melting, particularly in the shallow Arctic seafloor, where the hydrates are found only a few tens of feet deep. The more that sea or lake waters thaw the permafrost below, the more likely this cap is to blow suddenly, releasing jets of methane up through the water and into the atmosphere. A team that included two of Walter’s colleagues at Fairbanks found such plumes rising up from the shallow continental shelf of Siberia in 2008. Possibly, these releases have been happening for a long time, and we are only now noticing them. But the discoverers point out that the Siberian shelf alone holds an estimated 1.4 trillion tons of methane in the form of gas hydrates—equivalent to the newest estimates of the total greenhouse gases that would be released during a complete permafrost thaw.
Many researchers note that methane hydrates exist below the permafrost on land as well. The deposits are generally assumed to be too deep to be at risk of thawing. But that assumption, like others before it, has been cast in doubt. If Walter confirms indications from a field excursion earlier this year that Arctic lakes are tapping a methane source even older and greater than permafrost, her alerts would have to be cranked up considerably. And those bubbles she lights would take on an even more sinister glow.
More beasts, less burden: Large animals could help keep permafrost frozen.
Strangely enough, one way to slow the thawing of permafrost is to reintroduce massive herds of large, plant-eating animals to the Arctic landscape to mimic the days when millions of mammoths roamed the Siberian steppes. Although the idea may sound like science fiction, it is based in sound ecology. “Snow is like a down jacket that keeps the ground warm,” University of Alaska–Fairbanks researcher Katey Walter points out. “As the activity of animals compresses the snow or removes it through their foraging, the cold winter temperatures can penetrate deeper into the ground and keep the permafrost frozen.” Indeed, ecologist Sergey Zimov, director of the Northeast Science Station in Cherskii, Siberia, has hired local villagers to fashion that solution with their own hands. They have fenced off a 625-square-mile ranch Zimov calls Pleistocene Park and stocked it with moose, reindeer and Yakutian horses. Zimov has mimicked mammoths by driving around a military tank to crush the ground, too. He argues that the climate is still optimal for grassland, which would also insulate the permafrost below, if animals can thrive to cultivate it. Hunting, not climate, he points out, is blamed for the mammoth’s demise.
Note: This article was originally printed with the title, "The Peril below the Ice."