Today, 20% of Earth's land surface is locked up in a deep freeze. But scientists predict that air temperature in the Arctic is likely to rise as much as 6 degrees Celsius, or 10.8 degrees Fahrenheit, by the end of the century. That is expected to boost the emission of carbon compounds from soils.
"We are seeing thawing down to 5 meters," says geophysicist Vladimir Romanovsky of the University of Alaska. "A third to a half of permafrost is already within a degree to a degree and a half [Celsius] of thawing."
If only 1% of permafrost carbon were to be released each year, that could double the globe's annual carbon emissions, Romanovsky notes. "We are at a tipping point for positive feedback," he warns, referring to a process in which warming spurs emissions, which in turn generate more heat, in an uncontrollable cycle.
Walter's work is crucial, according to Romanovsky and others, because global warming hinges partly on the ratio of how much carbon is released as CO2 versus how much as methane, a molecule that contains both carbon and hydrogen. Methane, although a far more potent greenhouse gas than carbon dioxide, breaks down more quickly. But when it does, it oxidizes into a carbon dioxide molecule, which can last more than a century in the atmosphere.
Out on the lake, Walter explains: When organic matter (dead plants and animals) rots in the ground, it gives off carbon dioxide. Much of the organic material of thawed permafrost is expected to release carbon dioxide.
But as ice inside permafrost melts, small sinkholes open in the ground and fill with water, joining together to form millions of ponds and lakes. Organic matter slips from eroding shorelines to lake bottoms, where microbes feed on it. Because lake bottoms are oxygen-free, the microbes generate methane in addition to carbon dioxide -- as in the burping La Brea tar pits.
"These lakes are getting bigger -- in some places by a meter a year," Walter says, scooping out slush from the hole she has punched through 6 inches of ice. Into the seep, she inserts a plastic umbrella-like contraption fitted with a bottle to collect gas and a suspended brick to hold it straight.
Before Walter perfected the methane trap, when she was a graduate student in Siberia, she would swim in near-freezing water, dodging leeches and muskrats. Once she caught pneumonia. Another time, her hair caught on fire as she ignited a methane seep.
On the Seward Peninsula trip, she hikes up to 8 miles a day from lake to lake through snowdrifts. Her hip is black and blue from a fall through the ice. "Methane is hard work," she says with a smile.
At each seep, Walter places a small red flag so her colleagues can find the bubbles. Lawrence Plug, a geophysicist from Dalhousie University in Halifax, Canada; Guido Grosse, a German geologist; and Benjamin M. Jones, a U.S. Geological Survey researcher, help shovel off the ice in straight-line paths, take notes on the size of each bubble group, record the location with global positioning system devices, and measure the depth of the lakes.
In the evening, in a cramped cook tent, jars of peanut butter and Nutella sit amid satellite data maps and a textbook on "Applied Linear Statistical Models." Frosted hats and mittens drip from a clothesline. Jones cooks up a batch of hamburger as Walter labels methane bottles with a marker and enters data into her laptop.
Over the next two years, the researchers, funded by the National Science Foundation and NASA, will move between Siberia and Alaska. They will drill permafrost cores, map seeps and analyze data to produce a model of how methane from Arctic lakes might affect Earth's future climate.
"By figuring out how quickly permafrost thawed in the past, we can test our models to predict how fast it could thaw in the next 100 years," says Plug, who will make the complex calculations. "If the temperature warms a couple of degrees Celsius, the lakes could expand at two or three times their current rate."
Elsewhere, scientists cast a wary eye toward clouds of methane bubbles roiling the waters of the Siberian continental shelf. Those emissions, possibly from subsurface permafrost, are even harder to measure than lake emissions.
Meanwhile, researchers are debating the possibility of eventual seeps from methane hydrates -- icy formations beneath the continental shelves and the ocean bottom, and far below land-based permafrost.
Walsh, at the International Arctic Research Center, emphasizes the "huge range of uncertainty" as to how much climate change methane emissions could trigger. "The potential is there for large releases. But there is also a risk of alarmism."
To many Alaskans, it is hardly news that permafrost is thawing: Across the state, houses have been collapsing and trees tipping over. Researchers estimate that repairing affected schools, roads and bridges will cost up to $6 billion over the next two decades.
But the global implications have yet to sink in.
Out on the wild frontier of climate research, far from the legislatures and the diplomatic gatherings where climate policy is debated, Katey Walter and her colleagues focus on what they call "ground truthing."
And beyond that laborious data-gathering, Walter has a mission: to spread the word about what is happening. At the beginning of her field trip, she stops in Nome and leads a group of fifth-graders, many from Alaska Native tribes, out to poke holes in the ice of a nearby lake and light methane flares.
She talks to them about people who live in faraway cities, driving automobiles and working in industries that emit carbon dioxide. And how that causes warming that is felt in the Arctic. And why, even though there are so few people in Alaska, the ice around them is melting.
"That's what we're studying," she explains. "It's all related."
latimes.com /warmingSee video of Walter's research team as they drill through permafrost and ignite a