by Ned Rozell
February 25, 2006
Permafrost scientist Torre Jorgenson of Alaska Biological Research, Inc. was checking out an area west of the Colville River recently when he noticed water-filled pits that weren't in Navy photographs of the area from 1945.
"We were doing baseline studies on permafrost stability for ConocoPhillips and were looking at lake erosion, but when we saw the historical photos we said 'Wow, there's a lot going on here,"' Jorgenson said.
Matt Bray photo.
Ice wedges are underground chunks of ice about six to nine feet wide on top and then extend nine to 12 feet to a tapered end that points downward. They exist only in places where the yearly average temperature is well below freezing. Ice wedges form just below the layer of soil that freezes every winter and thaws each summer, and they endure longer than civilizations.
"For these to have developed over thousands of years, there had to be relatively stable temperatures," Jorgenson said. "Their thawing shows that today's temperatures are beyond normal fluctuations."
The ice wedges that are thawing on the North Slope are special features of a cold landscape, Jorgenson said, and are not to be confused with the deep permafrost locked in the soil beneath them.
"We're not talking about (typical) permafrost disappearing up there; it's still pretty cold permafrost and it's 600 meters (about 1,800 feet) deep in places," Jorgenson said. "It's not going to disappear anytime soon."
in recent years with the thaw ponds they leave behind.
Torre Jorgenson photo.
When working around the collapse pits, Jorgenson, Shur and Pullman also noticed "a violent degassing of methane." Methane, a greenhouse gas four times as effective at trapping heat than carbon dioxide, is in large supply in the frozen areas of the world. The gas is a product of decomposition of plants, and frozen ground locks it in.
"When we were walking in these troughs and stirring things up, the water was roiling with (methane) bubbles," Jorgenson said. "You can smell it escaping, and we've lit it with a match."
Thawing ice wedges up north
complicate what scientists think about greenhouse gases and the
Arctic. Some think arctic tundra has become a "carbon source"
that releases more greenhouse gases than it takes in. The collapsing
pits, which may someday cover up to 30 percent of the lowland
landscape, appear to release methane when they first collapse,
but then accumulate carbon as the wedges become overgrown with
sedges and peat, Jorgenson said.
Alaska Fairbanks, in cooperation with the UAF research community.
Ned Rozell [email@example.com]is a science writer at the institute.
Publish A Letter on SitNews Read Letters/Opinions