Not-So-Permafrost - Good Science News Article On Breakdown Of Subsoil Ice, Arctic Melt

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Daniel Fortier spends his summers studying the permafrost on Bylot Island, high in the eastern Canadian Arctic. While hiking there early in the 1999 field season, he distinctly heard the sound of running water yet saw no streams nearby. "I thought to myself, 'Where is this sound coming from?'" says Fortier. "So, like a good researcher, I started to dig." Excavating the soil, known as permafrost because its temperature is below 0°C year-round, Fortier tapped into a torrent-filled tunnel a meter or so below the surface. By tracking the water course uphill, he found its source: Large volumes of snowmelt had flowed into open fissures in the ground and had then melted a passage through a network of subterranean ice wedges that had formed over millennia (SN: 5/17/03, p. 314: http://www.sciencenews.org/articles/20030517/bob10.asp).

Eventually, the surprising tunnel grew so wide that its roof caved in, creating a gully that erosion then widened, says Fortier, a geomorphologist at the University of Alaska in Fairbanks. By the end of the summer, that gully was about 250 m long and 4 m wide. During the next 4 years, the network of underground tunnels at the site turned into a 750-m-long system of gullies that drained an area about the size of four soccer fields. Since then, Fortier and his colleagues have observed the same phenomenon at other sites on Bylot Island. Several teams of scientists had previously described similar networks of gullies at various sites in the Arctic, but those highly eroded features had been deemed as much as several thousand years old. "No one had ever seen one of these things forming," says Fortier. "We were in the right place at the right time."

Researchers are observing many new phenomena in the Arctic—most of them related to the world's changing climate. Globally, 11 of the 12 years from 1995 to 2006 are among the dozen warmest since the mid-1800s, scientists of the Intergovernmental Panel on Climate Change reported last month (SN: 2/10/07, p. 83: Available to subscribers at http://www.sciencenews.org/articles/20070210/fob1.asp). Average temperatures worldwide have risen about 0.7°C in the past 100 years, but those in the Arctic have risen even more. In high-latitude portions of Alaska and western Canada, average summer temperatures have increased by about 1.4°C just since 1961 (SN: 11/12/05, p. 312: Available to subscribers at http://www.sciencenews.org/articles/20051112/bob9.asp).

Those warmer air temperatures are significantly boosting soil temperatures in many regions, new studies show. Because the average annual temperature at many Arctic sites sits at or just below water's freezing point, even a small increase in local warming can have big consequences. Besides rendering underground ice wedges more susceptible to melting, the hike in temperatures threatens near-surface permafrost that has been in place since the height of the last ice age, about 25,000 years ago. Ecological changes, such as shifts in the patterns and timing of forest fires, further endanger near-surface permafrost. But researchers are still working out whether the permafrost will disappear over decades or millennia.

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http://www.sciencenews.org/articles/20070310/bob10.asp

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