The Continued Thawing of Alaska
The other day, I looked at something Alaskans rarely see but often feel, especially when it disappears--permafrost. Tom Osterkamp, who has studied permafrost for almost three decades, showed me how Alaska is changing as permafrost melts.
Osterkamp, a physics professor at the Geophysical Institute, and I drove to a place on the university campus where contractors were digging in preparation for a new section of road. At the edge of a hole large enough to fit a house, I watched a backhoe's bucket rumble through chunks of ice a few feet below the ground surface. The ice exploded under the teeth of the backhoe before quickly melting and adding to a shallow pool at the bottom of the hole. Osterkamp pointed to a white layer in the soil exposed by the backhoe. "That ice lens might go back several hundred feet," he said. "When it thaws, this road will look like that bike path over there." The bike path is sunken and cracked, bumpy as a motocross track. It's fun to ride on a mountain bike, but I wouldn't want to drive a car there.
Of course, most people in Alaska drive roller coaster roads all the time, an experience that will become even more common if air temperatures keep rising. In Alaska, it's hard not to build things on permafrost. About 85 percent of the state is underlain with some frozen ground. North of the Brooks Range, there's permafrost everywhere under the ground surface. It's more spotty south of the Brooks Range, where intermittent chunks of ice and frozen soil are found as far south as Anchorage. The worst sites contain ice-rich permafrost, lenses and wedges of pure ice that cause the ground to slump when they melt.
Much of the permafrost south of the Yukon River is within one or two degrees Celsius of thawing. Osterkamp said computer models call for an additional warming of 5 degrees Celsius in the next 50 years. Put the elements together, and the future of Alaska becomes pretty mushy.
The sinking of Alaska has already begun. Osterkamp gave the examples of Kipnuk, a coastal village so unstable that a marble placed on the school's floor rolls in unpredictable directions from year to year; and Deadhorse, an oil-field service town in which the slumping runway is being reconstructed because permafrost there has warmed about 4 degrees Celsius during the past decade.
The construction of roads and buildings can artificially induce permafrost melting, but the spontaneous collapse of the natural landscape is good evidence of a warmer climate. Again, Osterkamp has examples of how melting permafrost is affecting the natural landscape. In Mentasta Pass on the Tok Cutoff road, forests are being replaced by meadows of wet sedge, bogs, lakes and ponds. In the Tanana flats south of Fairbanks, birch forests above thawed permafrost are drowning. "It's changing the whole ecosystem," Osterkamp said. "Places that were birch and spruce forest are now islands of spruce and floating mats of vegetation." If forecasts of future warming turn out to be correct, melting permafrost will radically change the natural landscape. Mother Nature is pretty good at adapting; the change will be harder for the species that builds its homes, roads and pipelines on frozen ground.
