As Most Of Alaskan Interior's Permafrost Temps Reach 30 - 31F, Ground Begins Shift - FNM [View All]

[hatrack]

EDIT

According to Romanovsky, most of the permafrost in Interior Alaska is already near that threshold. It’s 30 or 31 degrees.

In general, permafrost exists in places where the annual average temperature is below freezing. But other factors also play a role. Mosses and plant matter help maintain permafrost by insulating the ground from warm air in the summer, and snowcover can actually degrade it by insulating the ground from cold air in the winter. The mean annual air temperature in Fairbanks is 27 or 28 degrees — at least 4 degrees below the temperature theoretically needed for permafrost. But the insulating snowcover has brought the frozen ground much closer to its tipping point.

At this site, the permafrost is both warming and thawing from the top down. Agricultural researchers cleared the area in the late 1930s, cutting down black spruce and removing any mosses that had built up. In the 70 years since, the permafrost has thawed down about 35 feet. In places nearby that weren’t cleared, the permafrost is still only a few feet down.

But if the ground is changing here because of human disturbance, it’s changing in other places simply because the air is getting warmer. From sites in Barrow, along the trans-Alaska oil pipeline, and in other places, scientists have documented an increase in the temperature of permafrost in Alaska of 2 to 5 degrees in the last 30 years. Records in Barrow show the permafrost was actually cooling in the 1950s and ’60s,when air temperatures were cooler, and started warming in the mid-’70s, when temperatures rose.

EDIT

http://newsminer.com/news/2008/jul/30/melting-permafrost-poses-threats-infrastructure-al/