Bubbles of warming,beneath the ice

Aquatic ecologist Katey Walter is struggling to understand and explain the complex science of Arctic methane—released due to the thawing of permafrost...

Published:March 8, 2009 4:41 pm

Aquatic ecologist Katey Walter is struggling to understand and explain the complex science of Arctic methane—released due to the thawing of permafrost—which is one of the factors accelerating climate change
Four miles south of the Arctic Circle,the morning sky is streaked with apricot. Frozen rivers split the tundra of the Seward Peninsula,coiling into vast lakes. And on a silent,wind-whipped pond,a lone figure,sweating and panting,shovels snow off the ice.

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 global climate change.

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 Programme last year. Large amounts entering the atmosphere,it concluded,could lead to “abrupt changes in the climate that would likely be irreversible.”

Methane has at least 20 times the heat-trapping effect of an equivalent amount of carbon dioxide. As warmer air thaws Arctic soils,as much as 50 billion metric tonnes 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. 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.

Methane levels in the atmosphere have tripled since preindustrial times. Human activities,including rice cultivation,cattle raising and coal mining account for about 70 per cent of releases,according to recent studies. Natural sources,including 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 also figure 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 realised before.”

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 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.

Nowhere is the evidence of a heating planet more dramatic than in the polar regions. Over the past 50 years,the Arctic has warmed twice as fast as the rest of the globe. Even as glaciers and sea ice have captured the most attention,growing concern is focused on the transformation of permafrost—soils that are frozen year-round.

Today,20 per cent 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 (10.8 degrees Fahrenheit) by the end of the century. That is expected to boost the emission of carbon compounds from soils.

The upper 3 metres (about 10 feet) of permafrost store 1.7 trillion metric tonnes of carbon,more than double the amount in the atmosphere today,according to a recent study in the journal Bioscience.

“We are seeing thawing down to 5 metres,” 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 per cent of permafrost carbon were to be released each year,that could double the globe’s current annual carbon emissions,Romanovsky notes. “We are at a tipping point for positive feedback,” he warns,referring to a process where 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 carbon dioxide,versus how much is released as methane,a molecule that contains carbon and hydrogen. Methane,although a far more potent greenhouse gas than carbon dioxide,breaks down more quickly. But when it does,it oxidises into a carbon dioxide molecule,which can last more than a century in the atmosphere.

Over the next two years,the researchers,funded by the US National Science Foundation and NASA,will move between Siberia and Alaska. They will drill permafrost cores,map seeps and analyse data to produce a model of how methane from Arctic lakes might affect Earth’s climate.

To many Alaskans,it is hardly news that permafrost is thawing: But the global implications have yet to sink in. 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 Native Alaskan 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.
_Margot Roosevelt,LATWP

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