The Tundra Thaw

THE TUNDRA LOOKS bleak in the long shadows that the morning sun is throwing from its usual midsummer spot near, but never below, the horizon.

Mosquitoes by the thousands are hovering expectantly around the camp, sensing a rare treat in a place where the nearest permanent human settlement is more than 300 miles away.

But as he slips on his rubber boots and adjusts his battered baseball cap, Gus Shaver declares the morning a fine one. An ecologist and senior scientist at the Marine Biological Laboratory in Woods Hole, Mass., Shaver has spent parts of his last 25 summers working in rugged conditions at the remote Toolik Field Station of the University of Alaska's Institute of Arctic Biology. And he speaks with the practiced enthusiasm of a North Slope veteran accustomed to dealing with visiting tyros who don't yet appreciate the subtle charms of life 150 miles above the Arctic Circle.

"What we have here is like a candy store! Every summer there is so much more to do than we can ever get to," Shaver says as he steps out of his laboratory trailer and into the ankle-deep mud of the camp. He grins and gestures toward distant clusters of scientific equipment that make the hillsides around Toolik look like a moonscape near an Apollo landing site. "Just look around-you can see there's so much going on."

His enthusiasm is not just a scientist's typical zest for field work. It's also based on his conviction, shared by many of the 200-plus researchers and students who rotate through Toolik during the summer months, that their experiments are playing an important role in explaining how global warming will change-and is already changing-life on Earth.

What they've found so far suggests that the tundra-a treeless, soggy grassland that is remarkably responsive to climate shifts-is evolving into something that may eventually resemble a birch and willow thicket. Even more importantly, they've also found evidence that the ecological changes now underway in the far north might not serve as a hoped-for brake on global warming, as many scientists have predicted. It's just as likely, the Toolik scientists say, that the tundra's makeover will end up accelerating disruptive climate changes throughout the world instead of slowing them down.

"The bottom line is, we're not going to be able to get out of this by planting more trees. These interactions are a lot more complicated than that," said George Kling, a biologist at the University of Michigan who spends his summers working at Toolik. "We can't count on nature bailing us out. There's no easy fix."

Tundra covers less than one-tenth of the Earth's surface, but it has an outsized impact on the future of the world's climate because of what's just below the surface.

Locked up in the frozen soil of arctic tundra and adjacent northern forests is a mother lode of organic matter, mostly dead plants, that includes massive amounts of nitrogen and carbon-about one-third of all the carbon on the Earth's surface, in fact. That's about as much carbon as is in the entire atmosphere, where carbon dioxide is the most important of the so-called "greenhouse gases" that contribute to global warming by acting like the glass panes of a greenhouse: they trap incoming solar heat and keep it from bouncing back into space.

For now, most of that carbon is still locked tight, and the tundra ecosystem still resembles a feeble garden planted in a few inches of barren soil on top of a hockey rink. A growing season only 10 weeks long assures that tiny native azaleas and rhododendrons will only just poke up through the cotton grass and lichen, and that willow and birch plants won't be more than a few inches tall. A pocket knife thrust into the soil at midsummer hits ice after only about 5inches, and the soil is so starved for nutrients that plants grow noticeably taller in places where arctic squirrels habitually defecate.

But there are signs that the tundra is changing. At Toolik Lake, the average summer temperature is about 6 degrees higher than 20 years ago, flowers are appearing earlier in the spring, and because of thawing the crusty upper edge of the permafrost layer is slightly deeper in the soil every year-a trend that should increase soil fertility as more organic matter unfreezes.

The big question is: Where will all that landlocked carbon go as the tundra metamorphoses and the world gets warmer?

Most of it may stay put if enough of the tundra's birches, willows and other scrawny woody plants start growing large enough to be bushy shrubs as temperatures rise, soil fertility increases and the growing season lengthens. That's important because those woody species are generally very efficient at accumulating and storing carbon in their stems and roots.

But researchers aren't sure whether the nascent shrubs will be able to keep up with the torrent of carbon that will be released as more and more organic matter-some of it frozen for centuries-starts to decompose in thawing tundra soils. If the woody plants can't keep up, then much of that newly released carbon may make its way into the atmosphere as carbon dioxide. That could be very bad news indeed, because more carbon dioxide in the air would, in turn, push temperatures higher and spur more melting and decomposition in the tundra, which would then release even more carbon dioxide.

In other words, in the coming century a bushy tundra might become an important brake on global warming-or it might become a crucial link in a runaway warming cycle that could cause wrenching changes throughout the planet.

Predicting the future is especially difficult because scientists aren't even sure whether the tundra right now is a net contributor or absorber of carbon. "You get fairly large spikes from year to year. In dry, warm years it will be a source, and in wet, cold years it'll be a sink," said Ed Rastetter, another Woods Hole-based researcher who also works at Toolik and has been trying to devise conceptual models of how carbon moves in the tundra ecosystem. "This year looks like a source year to me, but we're just guessing."

If Gus Shaver has the weight of a warming world on his shoulders this morning, he's not showing it. He bounds out of camp and into the tundra with his usual light-footed, bowlegged gait, keeping his center of gravity low and his feet on top of the squishy lumps of grass, called tussocks, that are ubiquitous in the tundra. Like coping with the unavoidable mosquitoes and sleeping in perpetual daylight, tussock walking is a skill that only the longest-tenured veterans of Toolik Lake have perfected.

Shaver's first destination this morning is a line of clear plastic tents perched on the side of a gentle slope overlooking the lake. For 12 years, he has been watching plants grow inside each tent, looking for clues about how the tundra will change in the warmer world of the coming century.

He ambles up to one of the tents, lifts its flap and offers a glimpse of the future. Inside, 3-foot-tall birches with bushy green leaves and tangled stems are growing thickly-a sharp contrast to the puny sedges and grasses that dominate the tundra just outside the tent.

Heat and especially fertilizer explain the difference. Inside the plastic tent, the average temperature is about 6 degrees warmer than outside, and the amount of nutrients in the soil is much higher thanks to annual additions of nitrogen and phosphorus fertilizer. The idea is to simulate growing conditions 50 to 100 years from now, when warmer temperatures will speed plant decomposition and greatly increase the amount of nitrogen available to plants.

Even the tents that haven't been artificially fertilized look at least slightly bushier inside thanks to the extra warmth, which is why Shaver says he and his colleagues "all foresee a future covered in birch on the North Slope-we just haven't figured out the timing yet."

At Shaver's next destination on the opposite side of the lake, the mysteries of the tundra's metamorphosis are in plain sight. On top of a hill, bounded by faded orange ribbon and weather-beaten wooden stakes, is an open- air section of tundra that Shaver has been regularly fertilizing for 20 years- one of the longest-running experiments of its kind anywhere in the world.

In the early years of the experiment, the tussock sedges and grasses remained dominant. But by 1989 the birches were starting to assert themselves, and by 1995 the plot resembled a forest-in-the-making. Then something unexpected happened. In the past few years, the birches have slowed and the grasses have again started to grow quickly, possibly because the birches can't utilize all the available nitrogen in the soil.

The re-emergence of the grasses is one of the reasons why, according to Shaver, the tundra may not be able to fulfill its hoped-for role as a brake on global warming-at least not until the birches are able to grow large enough to absorb large amounts of carbon, a process that could take decades.

"We think that first the tundra is going to be a carbon source, and then eventually it's going to be a carbon sink," Shaver said. "The question is: How long will that transition take? We just don't know."

As he spoke, another group of researchers a half-mile away were lugging a boxy metal-and-glass machine across a stretch of tussock tundra next to an abandoned airstrip used during the construction of the nearby Trans Alaska Pipeline.

The custom-designed machine, built from scavenged parts including a few small fans pulled off a broken-down microwave oven at a junkyard, is a novel attempt to figure out precisely where the carbon in frozen tundra will go when the world gets warmer.

This morning's activity beside the old airstrip is merely a dry run-the team of sweaty scientists carrying the machine hasn't yet gotten the regulatory approval it needs from Alaska environmental officials. When the machine is actually turned on, it will bombard a square meter of tundra with a precisely measured quantity of carbon-14 atoms, a radioactive isotope so rare in the natural world that the researchers will be able to trace precisely where every atom of it goes.

"We'll be able to measure where the carbon goes: whether it reaches roots, or goes above ground, or flows back into the soil," said Knute Nadelhoffer, the Woods Hole researcher who is leading the project. "It's going to help us figure out what's going to happen to all of that carbon stored in the tundra as the climate changes."

All around the crannied perimeter of Toolik Lake, in fact, groups of scientists are trying to predict how the tundra will change, each looking at the question from a different angle.

Not far from the water's edge, for example, Michigan's Kling has a group of graduate students on their hands and knees using large syringes to suck up groundwater from the tundra in an effort to measure how carbon dioxide moves through the tundra soils, and where it ultimately goes. What he's found so far suggests that much of the carbon dioxide that scientists had hoped was being absorbed by plants is actually moving into lakes and streams, and eventually into the atmosphere.

In the middle distance, beyond the lake's far shore, the brightly colored dots moving among the tussocks are the parkas and sweaters worn by teams of student researchers working for biologists Laura Gough of the University of Alabama and Sarah Hobbie of the University of Minnesota-Twin Cities. Employing a shoebox-sized gas analyzer, they're measuring the rate at which tundra plants are using carbon dioxide in hopes of figuring out why plants in acidic soils in the tundra use less than those in non-acidic soils-a sign that different types of tundra may respond to global warming in very different ways.

Nearby, in a quiet cove of the lake, John O'Brien of the University of Kansas has been trying to figure out what will happen to marine life in a warmer world. He's spent years curtaining off portions of Toolik and other lakes and measuring what happens when he adds nitrogen-a predicted effect of global warming, since organic matter in the thawing tundra will decompose faster and send nitrogen into nearby lakes.

His experiments suggest the region's numerous lakes may be able to absorb some of the excess nitrogen for a while, and fish may grow bigger because of it. But eventually, he believes, those lakes will be so saturated with nutrients that they will become choked with algae, which in turn will soak up so much dissolved oxygen that some important fish species, especially lake trout, may not survive.

And up on top of a nearby hill overlooking Toolik, a solitary scientist in a big floppy hat is crouching on a narrow wooden plank, trying to avoid stepping on any of the tiny plants she is painstakingly measuring with a ruler. Syndonia Bret-Harte, a post-doctoral researcher affiliated with the University of Alaska, has been working on the hill for four mosquito-filled summers, removing or adding various types of plants in no fewer than 102 marked plots to find out which combination is likeliest to thrive in the 21st Century.

"It's a big puzzle, and we don't know how all the pieces fit together," she said, pausing to swat away a bug and adjust her hat. "But we do know there is the potential for some pretty dramatic and far-reaching effects from climate change, and that makes the work interesting.

"I mean, why else would we do this?"

A Mecca for Researchers

IT'S MIDNIGHT, and Tara Madsen has finished her sauna and is headed for work. The 20-year-old undergraduate from Florida International University in Miami will spend the next eight hours on her hands and knees, absorbed in the monotonous work of measuring gas fluxes from tundra plants.

She won't need a flashlight.

The sun won't go down, and neither will the mosquitoes, during Madsen's long shift on the tundra. She won't be alone: Just over the next hill, another group of students will be working on a similar project, while back at camp the microscopes and computer terminals in the laboratory trailers will stay busy long after midnight.

For much of the year, Toolik Lake is a sleepy and sparsely populated place, but during June and early July it becomes a scientific Brigadoon. Researchers and students work at a frenetic pace, cramming as much work as possible into their short stays.

Money and weather explain the frenzy. At $ 160 per day, the rent that the University of Alaska charges each Toolik resident for food, shelter (tents or trailers) and lab space isn't cheap. There's enough space for only about 70 people at a time, and the weather can be bitterly cold as late as mid-June and as early as August.

Presiding benignly over the bustle is John Hobbie, an aquatic biologist who first prospected Toolik as a possible research site in 1975.

As co-director of the Ecosystems Center at the Marine Biological Laboratory in Woods Hole, Mass., Hobbie oversees about $ 2 million worth of MBL research at Toolik every year, almost all of it funded by grants from the National Science Foundation. MBL projects are about 60 percent of the total research budget at Toolik, but the site also attracts arctic researchers from as far away as northern Europe, Japan and Russia.

While Toolik is a mecca for top-flight tundra biologists around the world, most of the field work there is actually done by students lured to the High Arctic by the prospect of an adventurous summer.

The physical setting is indeed inspiring, with vistas of glassy lakes and spectacular mountains in every direction. But it is also extremely isolated. At Toolik Lake, the telephone is for emergencies only, and there's no television, fresh newspapers or Internet browsing (e-mail was installed just last year).

More significantly, much of the work that the students do at Toolik is numbingly tedious. Their noisome tasks-many of which are memorialized in graffiti on the walls of the camp's fetid outhouse-include "plucking" and "sucking."

Plucking is the dissection, stem by minuscule stem, of individual sections of tundra dug up in chunks and hauled to laboratory tables for dismemberment. Sorting the contents of just one 6-by-6-inch square takes about eight hours.

Sucking is, if possible, even more aggravating. It requires inserting a large plastic syringe into the ground and sucking out exactly 500 milliliters of groundwater without allowing any air bubbles to contaminate the sample. It can take a dozen or more tries to get one clean sample, and during a typical summer students will collect more than a thousand samples for analysis.

Other students at Toolik spend their days and nights painstakingly measuring the growth of tiny arctic plants or, like Madsen, lugging heavy "portable" machines around the tundra to analyze the carbon dioxide content of soil, air and plants.

Understandably, Toolik people are intense about their playtime, too.

July 4 features a "dare to be stupid" parade in which the winners tend to be both inebriated and clothing-free. Daylong hikes into the Brooks Range and midnight walks in the hills near camp are also popular, but the favorite diversion at Toolik is the lakeside sauna.

Rebuilt by hand after a fire about 10 years ago, the wooden sauna features a precarious diving board that truly deranged researchers-young and old-use to hurtle themselves into the freezing lake after heating up in the sauna.

Needless to say, a line forms there every night.

-Dan Fagin

An Outdoor Laboratory

YOU CAN'T HELP feeling a little sorry for the tundra at Toolik Lake.

Yes, it's smack dab in the middle of hundreds of thousands of square miles of untouched Alaskan wilderness. But the landscape at Toolik-or small chunks of it, anyway-literally gets torn to shreds every summer.

Researchers not only dig up and meticulously dissect pieces of local tundra, they also fertilize it, soak it, shade it, warm it, transplant it, suck up its groundwater with giant syringes and even bombard it with radiation-all in the name of hands-on science.

Even the arctic ground squirrels that hang around the camp are altered for research purposes. Many of the sik-siks, as the squirrels are called by native Inuits, have transmitters implanted in their bellies to monitor how their metabolism changes during the long and perpetually dark Alaskan winter.

By transforming Toolik into an outdoor laboratory, the ecologists who come here every summer hope to answer some important questions about how all of the components of the arctic ecosystem fit together. How much extra watering does it take to change the mix of grasses and wildflowers growing here? Are arctic plants tiny because of too little sunlight or too few nutrients in the soil? What will happen to the tundra if the temperature rises by 5 degrees over the next century?

The search for answers is an intrusive, labor-intensive business, which is why the area around camp at Toolik is dotted with clusters of tents, chambers, hoses, fences and other portable devices used in experiments that manipulate the amount of heat, light, moisture and minerals that reach the soil.

Tweaking the tundra is the best way to understand how the ecosystem really works, scientists say, and it's also the best way to test ideas about how the tundra will change if global warming continues as expected.

"Manipulating ecosystems experimentally is a wonderful tool for determining what will happen in the future," said aquatic biologist John Hobbie, who has overseen much of the research at Toolik for the past 26 years. "How are we going to look into the future without doing these manipulations? We can change each of these factors and see what's really going to happen."

What makes the tundra such an inviting place for such experiments is its simplicity. Because the growing season lasts a scant 10 weeks, very few plant species can live there-only 12 different leafy plants, for example, are found in one common type of tundra. And because the layer of thawed soil above the permafrost is only about 5 inches deep at midsummer, water and nutrients never travel very far.

That simplicity makes it much easier for ecologists to study how different parts of the tundra ecosystem respond to an experiment. Like a machine with few moving parts, the tundra ecosystem is much easier to keep track of than is a rain forest, where plotting the interactions of thousands of species is an intractable scientific problem. "You could never do this kind of work in the tropics. There are just too many species," said Syndonia Bret-Harte, a biologist.

Another bonus for Toolik researchers is its isolation, which means the tundra has never before been disturbed by humans. "This place really hasn't changed for 10,000 years" since the departure of the last glacier, said Hobbie.

Just as importantly, the camp's remote location means there's little reason for anyone to object to, or interfere with, their experiments. "Very few scientists have the ability to just go flipping things around the landscape," said John O'Brien of the University of Kansas, whose experiments include fertilizing local lakes and adding or removing fish and small crustaceans. "Here, no one cares."

Actually, strict land-use rules are enforced by the federal Bureau of Land Management, which ultimately controls the land at Toolik. And O'Brien and the other researchers there take pains to minimize their impact on the landscape, spending days building walkways of elevated planks to keep their feet off the tundra as they go back and forth between camp and their experimental sites.

More importantly, the Toolik scientists have discovered that the fierce arctic climate is an inexorable force that quickly erases the marks left by their experiments. The lake, stream or land where a project took place invariably reverts to its natural condition within a few years, they say.

"What we do is to punch an ecosystem and see how it responds, and then, just as importantly, we see how it comes back when we're done," said O'Brien. "We've learned the ecosystem is pretty forgiving of these manipulations."