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The Arctic Thaw Could Make Global Warming Worse

The melting Arctic is releasing vast quantities of methane. How big is this greenhouse threat? What can be done?

Double the Emissions
Some Arctic scientists are quick to point out that certain environmental changes could slow warming rather than speed it up, however. Sturm has also found areas where shrubs are not expanding and soils are colder. In other regions, the conversion of mossy tundra to thin forest, not shrubland, offsets some rise in greenhouse gases by storing more carbon in trees. Still, the consensus is that warming will dominate. “The question is whether this is a weak positive or a strong positive,” Lawrence says. “It may take a long time to get the numbers right.”

Even now, though, Lawrence is willing to offer a lower bound of methane release. It is easy, he says, to envision conditions that double methane emissions from the Arctic by the end of the 21st century simply by activating more microbes in those uppermost few feet of Arctic soil that thaw every summer, the so-called active layer. But more lakes formed because of thawing would send that estimate skyrocketing. Walter’s work suggested that the lakes near Cherskii expanded significantly between 1974 and 2000 and that as they did, they ate into the permafrost along their shorelines. She found that methane rises up most vigorously at these outer edges, which fueled her 2006 estimate that an expansion of thaw lakes increased methane emissions in the region by 58 percent.

Going back to Siberia as a professor in 2008 made her wonder if it was time to update that estimate. The banks of the lake where she lit her first methane bubble in 2002 had advanced greatly. “The dramatic changes to my study sites really made my eyebrows go up,” she says. “I couldn’t even recognize the lake margins. Some ponds appeared to have doubled or tripled in size.” If other lakes experienced similar growth they may have contributed to the global methane spike that began two years ago.

Walter still spends four months or more each year walking the lakes in dogged pursuit of answers. Her collaborators and study sites have expanded considerably. To date, she and her colleagues have visited 60 lakes in Siberia and Alaska, but that is still only the tip of the proverbial iceberg. With no hope of visiting every Arctic thaw lake in person, her team is now working on a technique to spot methane seeps from space. One new high-resolution German satellite, TerraSAR-X, is making it possible to identify distinct patches of bubbles on the surfaces of frozen lakes—and to keep track of which patches are growing.

One More Reason to Cut Back
Once a given helping of permafrost starts to thaw and a gas leak starts, not much can be done about it. Local villages could capture the bubbling methane gas and use it to replace diesel fuel (technologies already exist for capturing methane released from landfills). But that is a “very small fix,” Walter concedes. The only real solution is to slow the thaw itself.

Those of us living at lower latitudes can make the greatest difference. The model linking permafrost thaw to loss of sea ice predicts that both processes could be slowed considerably if humanity stabilizes CO2 emissions soon, slowing the atmospheric warming that is generating the methane. “It’s not a runaway train,” Lawrence says. Not yet, anyway, Walter and others warn. Lawrence sounds optimistic when he says, “Perhaps we have to reduce emissions by 80 percent rather than 70 percent by 2050.” But such dramatic reductions won’t be easy. Since 2000 human activities have raised CO2 concentrations much faster than expected.

Even if humanity finds the resolve to slow warming, too much thawing in the wrong place could tap submerged caverns of methane. Just below the permafrost layer in many locations lurk large pockets of pure gas that formed millions of years ago. Some of the pockets are run-of-the-mill natural gas reserves, but others are so-called methane hydrates, massive deposits of ice that contain large amounts of gas within their crystalline structure.

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