Methane is emitted anywhere organic matter ferments—be that a cow’s belly or frozen soil that starts to thaw. Permafrost, which averages 80 feet thick, is chock-full of dead plant and animal matter that has been locked in cold storage for thousands of years. Conventional wisdom long held that permafrost should take thousands of years to melt away, so researchers expected it to play a negligible role in climate change. But recent findings—Walter’s lake discovery in particular—have wrecked that prediction.
Walter’s work revealed that the relatively warm lake bed was indeed thawing the frozen earth directly below it, down several dozen feet. Thawing a block of permafrost is like taking a package of frozen hamburger out of the freezer and leaving it on the kitchen counter. As the meat warms, ravenous microbes consume it, giving off a gas as a by-product. On dry land, microbes convert the dead animal and plant matter primarily into CO2. But in the wet, oxygen-starved depths of a lake, they instead release methane. Walter’s best guess is that researchers have been underestimating methane emissions from Arctic wetlands by as much as 63 percent.
This methane alert, which Walter raised first in her doctoral thesis, captured the attention of the U.S. Council of Graduate Schools, which in 2006 granted her the nation’s most prestigious honor for doctoral dissertations. She credits her discovery to living lakeside from one season to the next. Most scientists tend to be in the field only during the summer, when the bubbling seeps of gas are hard to spot in open water, or in the winter, when the lake is buried under six feet of snow. The same camouflage deterred Walter until that overcast afternoon in October 2002, when she decided to remain lakeside during Siberia’s brief transition from summer to winter. By the spring of 2003 she knew exactly what she needed to do: place her gas traps directly over known seeps. Her results have since riveted attention on how drastically thawing permafrost could speed up global warming.
Trapping the Demon
During four years of doctoral work, Walter spent 20 months in the Siberian wilderness, often alone or with only one loyal field assistant. She hiked up to eight miles a day across sodden tundra and braved icy waters on several occasions, deliberately as well as accidentally. She knew exactly what she was getting into; as a high school exchange student to Russia nine years earlier, Walter had learned the language and was deeply touched by the harsh conditions of post-Soviet life. She jumped at the chance to return.
Headquarters for much of those four years was the so-called Northeast Science Station, a small outpost in Cherskii, about 90 miles south of the Arctic Ocean. The station’s director, legendary ecologist Sergey Zimov, who had published his suspicions about the role of lake emissions in climate change, helped to define Walter’s straightforward goal: find a way to quantify the methane release and determine what fraction could be attributed to thawing permafrost. Walter’s first challenge was to invent a way to capture the gas. She knew she would eventually need hundreds of contraptions to adequately sample the two large lakes in her study, so her design needed to be simple—and cheap. Walter and her Siberian field assistant spent weeks cobbling together traps in the station’s cramped attic, mostly from recycled trash they found at abandoned Soviet military bases and along dusty dirt roads. For each trap, they secured an inverted plastic bottle to the center of an umbrella-shaped plastic skirt, which was held open by a hoop of wire to funnel bubbles upward. They made 75 of them in all.
During her first excursions, Walter dutifully placed the traps randomly across the lakes’ unfrozen surface, according to standard scientific protocol. “We put a lot of hard work in that, and I was frustrated,” Walter says. “We could see the bubbles, but we weren’t catching much gas.” It wasn’t until she walked out onto the freshly frozen ice for the first time and saw the disparate collections of bubbles that she realized the methane was rising up at discrete points. She made an executive decision, a bit nervously and without the consent of her thesis advisers, to set the traps directly over seeps when the lakes thawed the following spring. So, in 2003, she set about anchoring many of her traps right near the lake bottom—a job that called for a snorkel and wet suit. Locating a seep and setting the necessary tripod of weights and ropes for a single trap required two and a half hours submerged in lake water still gripped by winter chill.