Arctic Dispatch: A Thaw in the Arctic Tundra

Researchers at the Toolik Field Station study thermokarst to understand the ecological effects of climate change

William Bowden

Knee-deep in the muddy shambles of collapsed Alaskan tundra, Elissa Schuett points to the remains of a cavern that she was able stand in last summer. Today, it is gone, gobbled up by the gaping maw known as a a thermokarst that continues to march outward as the land rapidly melts.

Thermokarst failures occur when permafrost—a layer of frozen soil in Earth's polar regions—thaws and becomes unstable. Though the events occur naturally throughout the Arctic, many scientists suspect that rising temperatures in the north are causing more of these features to form. By comparing aerial photographs from 1985 with recent photos, "We can now say with some assurance... that in some locations [there are] between two and five times more of these features now than in the early 1980s," says William Bowden, an aquatic ecologist at the University of Vermont.

That's why Bowden, his research assistant Schuett, and others at Toolik Field Station, a University of Alaska, Fairbanks, research facility 150 miles north of the Arctic Circle in northern Alaska, are studying the impact of thermokarsts on the environment. Their work fits into a long tradition of climate change research at Toolik, which, since its founding in 1975, has provided a pristine laboratory for studying how a warmer world will transform the land and waterways of the Arctic.

Understanding climate and environmental change, according to Norman Marcotte of Canada's Natural Sciences and Engineering Research Council, is the "burning issue" in Arctic research internationally. Research stations such as Toolik are key in capturing long-term data and exploring issues in the field, he says by e-mail, and Canada has plans to develop an Arctic research station with many of the same elements as Toolik.

Though much of Arctic research has focused on observing the environment, "At Toolik we're able to go deeper into that" and "study what's actually controlling all these processes," says Toolik co-founder John Hobbie, a senior scholar at the Ecosystems Center of the Marine Biological Laboratory in Woods Hole, Massachusetts.

It's also "the only place in North America where we can see or get an advanced view of how climate change can affect ecosystems," he adds.

And in many ways, climate change has already begun reshaping this dichotomously fragile and hardy land. Between 1966 and 1995, Arctic temperatures increased .7 degrees Celsius per decade, a trend that puts "northern Alaska in the hot seat," says Syndonia Bret-Harte, Toolik's associate science director. The Arctic is warming faster than even the tropical areas of the world: Spring arrives earlier, fall sets in later, and the temperature of the permafrost in many areas, including Toolik, hovers perilously close to the zero-degree Celsius tipping point. That's when the frozen soil that gives the tundra its backbone could crumble away.

New thermokarsts in Alaska could also show how warming may change streams or lakes, since these features often occur near water. When a thermokarst was discovered in 2003 near the Toolik River, Bowden and colleagues found it had dislodged so much sediment into the river that the water turned muddy 40 kilometers downstream. He and his colleagues also reported in June 2008 in the Journal of Geophysical Researchthat ammonium, nitrate, and phosphorus emitted from that collapse will over time "significantly alter the structure and function of the river."

For Bowden and other Toolik researchers, such observations were familiar. Between 1983 and 2004, they saw how drastically phosphorus could restructure a river in an experiment done on the Kuparuk River near Toolik—"the best studied river basin in the whole Arctic," according to Hobbie. In that experiment, scientists added small amounts of phosphorus, a nutrient common in fertilizer and residential and industrial pollution, to the river each summer. After eight years, moss expanded in the river, crowding out other plant species and sparking a growth in certain types of insects. Productivity overall in the river boomed. This investigation may foreshadow what happens when permafrost melts and nutrients are freed into the air and water.

On land, Toolik researchers have also added fertilizer to different types of tundra. In an experiment operating since 1989, Ecosystems Center senior scientist Gaius Shaver has found that on tussock tundra, some deciduous shrubs, such as dwarf birch, can capitalize on the influx of nitrogen and phosphorus by increasing in abundance and reducing species diversity. Toolik scientists are also focused on why the Arctic seems to be greening, Bret-Harte explains. It may be due to more shrubs: About 12,000 years ago when the climate was warmer, shrubs dominated the landscape, she said.

Though these polar shifts may seem isolated from the rest of the world, a melting Arctic could accelerate climate change. Bret-Harte points out that Arctic landmasses—including the boreal forests—hold nearly 40 percent of the world's soil carbon, but make up only one-sixth of Earth's land area. If the carbon locked up in the soil is released by melting permafrost, she says, it could more than double the concentration of carbon dioxide , a major greenhouse gas, in the environment .

Bowden of the University of Vermont believes there is "strong evidence" that trapped carbon and methane could be set free during thermokarst events and contribute to warming. He is seeking funding to investigate how thermokarsts will influence Arctic ecosystems overall. For instance, a thermokarst that causes a spike in sediments in waterways may suffocate plants, clog fish gills, and ultimately set off a cascade of effects all the way up the food web.

"It's not a horror story—it's not like this is not a natural process," Bowden cautions. "But I think there's strong evidence that [human] influences that are some distance away from Arctic are having these secondary effects... which are going to be potentially very important in structuring the way the Arctic landscape looks and behaves in the future."