The young woman with curly reddish hair stops, scribbles data, snaps a photo, grabs a heavy metal pick and stabs at white orbs in the thick black ice.
"Every time I see bubbles, I have the same feeling," says Katey Walter, a University of Alaska researcher. "They are amazing and beautiful."
Beautiful, yes. But ominous. When her pick breaks through the surface, the orbs burst with a low gurgle, spewing methane, a potent greenhouse gas that could accelerate the pace of climate change across the globe.
International experts are alarmed. "Methane release due to thawing permafrost in the Arctic is a global warming wild card," warned a report by the United Nations Environment Program last year. Large amounts entering the atmosphere, it concluded, could lead to "abrupt changes in the climate that would likely be irreversible."
Methane (CH4) has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide (CO2). As warmer air thaws Arctic soils, as much as 55 billion tons of methane could be released from beneath Siberian lakes alone, according to Walter’s research. That would amount to 10 times the amount currently in the atmosphere.
At 32, Walter, an aquatic ecologist, is a rising star among the thousands of scientists who are struggling to map, measure and predict climate change. Parts of her doctoral dissertation on Siberian lakes were published in three prestigious journals in 2007: Science, Nature and Philosophical Transactions of the Royal Society.
According to one of her studies, methane emissions from Arctic lakes were a major contributor to a period of global warming more than 11,000 years ago.
"It happened on a large scale in the past, and it could happen on a large scale in the future," says Walter, who refers to potential methane emissions as "a time bomb."
Methane levels in the atmosphere have tripled since preindustrial times. Human activities, including rice cultivation, cattle raising and coal mining, account for about 70% of releases, according to recent studies. Natural sources, like tropical wetlands and termites, make up the rest. But those estimates had not incorporated the bubbles Walter was probing on an autumn morning on the Seward Peninsula.
That gurgling gas could change the entire model for predicting global warming. And lakes are not the only methane source: Newly discovered seeps -- places where methane leaks to the surface -- from the shallow waters of Siberia's vast continental shelf are also likely to upset previous assumptions.
Walter's work "has gotten a lot of attention," said John E. Walsh, chief scientist of the International Arctic Research Center in Fairbanks. "She found direct evidence of methane releases in high-latitude lakes. That was not fully realized before."
In a field where the science often seems opaque, Walter's research has a flashy side. She enjoys igniting methane seeps with a cigarette lighter, leaping away as the gas flares as high as 20 feet.
"It's fun," she says. "And it is informative."
Videos of the stunts have swept through the Internet, rare visual evidence of possible danger ahead. At a recent Senate hearing, Al Gore played a clip of her lighting a methane seep. The BBC, the Discovery Channel and the History Channel have featured her in documentaries.
But the complex science of Arctic methane is only beginning to be understood. In the desolate wilderness of the Bering Land Bridge National Preserve, a sense of urgency is palpable among Walter and three fellow researchers, hunkered down in neon-orange tents.
An occasional helicopter ferries supplies from Nome, the closest town, soaring over scattered herds of caribou. A red fox scampers through the brush. Across a snowfield, bear tracks recede into the distance, a reminder that field science isn't for sissies.
"Can you shoot a gun?" Walter asks a visitor, as she heads out to one of 20 lakes she is surveying. When the answer is noncommittal, she hands over bear spray and instructs: "Don't use it until the bear is right up close, facing you."
Nowhere is the evidence of a heating planet more dramatic than in the polar regions. Over the last 50 years, the Arctic has warmed twice as fast as the rest of the globe. Last summer, for the first time in recorded history, the North Pole could be circumnavigated. Ice sheets on Greenland and West Antarctica are melting rapidly. Polar bears and emperor penguins are threatened with extinction.