TELLER, Alaska _ An unpaved highway runs north out of Nome, carving through more than 70 lonely miles of tundra before dead-ending at this Inupiaq village.
Maintenance crews keep the route open during the summer months. The work has become increasingly costly as a layer of ice and frozen dirt under the road softens into soggy muck, and stretches of road bed crack and collapse.
"There is so much melting. We just keep having to haul in gravel," said Calvin Schaeffer, of the Alaska state Department of Transportation.
Alaska's permafrost is under assault from a warming climate, and it's happening a lot faster than anticipated. Hillside slopes have liquefied, unleashing slides that end up as muddy deltas in salmon streams. The ground under the Nome airport runway _ key to linking the community to the outside world _ has thawed, requiring costly patches. And during the hottest July on record, a sinkhole 14 feet deep opened along a main roadway in the city.
For a region where climate change also is bringing profound changes offshore, these are disruptive developments. As the northern Bering Sea warms, bird and marine mammal die-offs are on the rise and winter ice is on the decline, enabling storms to gain strength over open water and slam into coastal communities like Teller.
The accelerating melt is a global concern: Permafrost, which mostly lies in the northern reaches of the planet, is a vast carbon storehouse of frozen plants and animals that release greenhouse gases as they warm and decompose.
Fossil fuel combustion still is the main source of greenhouse gas emissions driving climate change. But the world's permafrost now releases 1.2 to 2.2 million metric tons each year _ at the upper end, nearly equal to Japan's greenhouse gas emissions, according to a report this month by the National Oceanic and Atmospheric Administration. Later this century, these emissions are expected to exceed those of the United States.
Scientists who study permafrost already are noticing some striking changes in Alaska's landscape.
Canadian scientist Merritt Turetsky monitors tracts of interior Alaska permafrost that a decade ago were covered by spruce forest. That land is now covered with lakes.
"It can happen super quickly, even in a matter of months. ... This has been a wake-up call to the climate-science community," Turetsky said. "What has been happening at some of our field sites is a whole different ballgame."
