Is Arctic permafrost the "sleeping giant" of climate change?

Philly.com: It's a sight Miller won't soon forget. Flying low and slow above the pristine terrain of Alaska's North Slope research scientist Charles Miller of NASA's Jet Propulsion Laboratory surveys the white expanse of tundra and permafrost below. On the horizon, a long, dark line appears. His plane draws nearer, and the mysterious object reveals itself to be a massive herd of migrating caribou, stretching for miles.

"Seeing those caribou marching single-file across the tundra puts what we're doing here in the Arctic into perspective," says Miller, who is on five-year mission named “CARVE” to study how climate change is affecting the Arctic's carbon cycle. CARVE is short for the “Carbon in Arctic Reservoirs Vulnerability Experiment.”  Now in its third year, the airborne campaign is testing the hypothesis that Arctic carbon reservoirs are vulnerable to warming, while delivering the first source-maps of greenhouse gases carbon dioxide and methane.

About two dozen scientists from 12 institutions are participating. "The Arctic is critical to understanding global climate," says Miller. "Climate change is already happening in the Arctic, faster than its ecosystems can adapt. Looking at the Arctic is like looking at the canary in the coal mine for the entire Earth system." Over hundreds of millennia, Arctic permafrost soils have accumulated vast stores of organic carbon - an estimated 1,400 to 1,850 billion metric tons of it.  That's about half of all the estimated organic carbon stored in Earth's soils.

In comparison, about 350 billion metric tons of carbon have been emitted from all fossil-fuel combustion and human activities since 1850. Most of the Arctic’s sequestered carbon is located in thaw-vulnerable topsoils within 3 meters of the surface. But, as scientists are learning, permafrost - and its stored carbon - may not be as permanent as its name implies. And that has them concerned. "Permafrost soils are warming even faster than Arctic air temperatures - as much as 1.5 to 2.5 degrees Celsius in just the past 30 years," says Miller. "As heat from Earth's surface penetrates into permafrost, it threatens to mobilize these organic carbon reservoirs and release them into the atmosphere as carbon dioxide and methane, upsetting the Arctic's carbon balance and greatly exacerbating global warming."...

From August 1973: Patterned Ground Shows Ice Polygons (Lattice Outlines) and Typical Summer Arctic Tundra. Patterned Ground, Ice Polygons, and Permafrost Are Found Along the Entire Route of the Line, Although They Are Relatively Rare South of the Yukon River. Alaska (US state). Environmental Protection Agency, Project DOCUMERICA.