University of Vermont

William “Breck” Bowden, who has been studying Alaskan streams and their relation to the landscape since 1987, contributed to the Arctic Climate Impact Assessment released this week. The landmark four-year report from 300 scientists concludes that Arctic temperatures are rising twice as fast as the rest of the Earth, and within a century 50-60 percent of the ice will become water.

“I believe this report is one of the most cogent arguments making the case for warming in the Arctic,” says Bowden, who is the Patrick Professor of Watershed Science and Planning at the Rubenstein School of Environment and Natural Resources and Director of the Vermont Water Resources and Lake Studies Center. “It’s no longer ‘if’ and it’s no longer ‘when.’ It’s occurring now. We now have statistically supported evidence to say global warming is happening. The key questions now are ‘how much?’ and ‘with what impact?’ ”

As part of the National Science Foundation Arctic Long-Term Ecological Research program, a consortium of about 100 researchers at several sites worldwide that are considered important biomes, Bowden has seen his work transition from trying to decipher the workings of a little understood biotic community, to grappling with the consequences of warming on resources and the indigenous plants, animals and people.

Bowden and others based at the Toolik Lake Field Station, about 130 miles south of Prudhoe Bay and 350 miles north of Fairbanks, analyze the changing landscape. This area has been a research subject continuously since the 1970s and other records go back to the 1920s and 30s. Undergraduate and graduate students travel with him, often staying during the research season May-September while Bowden typically visits two to four times a year.

Because the Alaskan Arctic is warming faster than any other place in the world, it offers a fast-track laboratory to study climate change. While the rest of the world has warmed about one degree over the past century, the Arctic's ice and snow magnifies temperature changes and the bare terrain starts absorbing heat. Computer models predict that during the next century the Arctic will warm an additional 7 to 12 degrees Fahrenheit.

The researchers at Toolik Lake have measured steady lake temperature increases and snow decreases for years, but in August 2003 Bowden's team found something new and dramatic: a gaping hole in the permafrost as long as a football field, half as wide and 8-10 feet deep, whose surface eroded and washed down the nearby Toolik River. The cave-in is called a “thermokarst.”

“Often portions of an entire hillslide will slip off but in this one, it really surprised us at the time, a tunnel had formed, collapsed and caved in down the slope. The bottom fell out of the stream,” Bowden says.

Last summer’s trip was more startling.

“We noted at least two new thermokarsts with failure modes similar to the one observed in 2003 along with numerous slip failures. Although the terrestrial area impacted by these thermokarsts is limited, the aquatic habitat altered by these failures is extensive. It is likely that warming in the Arctic foothills region will lead to additional and perhaps accelerated thermokarst formation which may have considerable impacts on aquatic ecosystem over wide areas and at least decadal time scales,” he and colleagues told the American Geophysical Union Fall Meeting in San Francisco.

That means that while thermokarsts look small against the vastness of the Arctic, their sediment washing down a river can measure a half-inch deep 20-30 miles downstream. It appears that accelerated warming will lead to more of these arctic mudslides that smother moss, algae and other life.

“This a phenomenon we have not observed in our 30 years on the site — but in the last two years we’ve discovered a dozen in the wider area. We need to be able to identify them automatically in a wider spatial area and to determine if these are new,” he says. Thermokarst study may emerge as a separate focus as the team pursues the possibility of tracking them by remote sensing and aerial photography.

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