Permafrost thawing

(CBS) -- For the past decade, Sue Natali of the Woods Hole Research Center has been taking trips deep into remote corners of Alaska's wilderness. Her mission -- monitor how the region's warming air temperatures are impacting the frozen earth underground.

"Permafrost is frozen ground, it's ground that remains below Celsius for two or more consecutive years."

But that term is actually misleading because the icy soil buried under this spongy moss is anything but permanent.

Recent studies show arctic permafrost has warmed by up to two degrees Celsius in the past three decades, and predict that 20% of it may thaw by 2040.

Natali uses a drill to extract permafrost, which starts a few feet under the surface and can extend hundreds of feet down. It contains organic material from dead and partially decayed plants and animals.

Some of it has been frozen for thousands of years, but as it thaws, that organic material releases gases like methane and carbon dioxide - so-called greenhouse gases that warm the atmosphere.

"Our projections say for the larger permafrost region, we can expect 150 billion tons of carbon to be released by 2100."

Based on current emissions, the U.S. is already expected to release that much carbon over the same time period just by burning fossil fuels. This thawing permafrost would effectively double that figure.

The best view of permafrost does come from underground, in a 50-year old tunnel built and maintained by the U.S. Army Corps of Engineers just outside Fairbanks.
Down there, it's easy to visualize another danger posed by thawing ground.

"You can imagine if this -- the permafrost-- thaws and this really large ice wedge here melts out, that you're going to have some pretty substantial ground collapse."