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On the Stability of the Planet's Permafrost
Reference
Froese, D.G., Westgate, J.A., Reyes, A.V., Enkin, R.J. and Preece, S.J. 2008. Ancient permafrost and a future, warmer Arctic. Science 321: 1648.

Background
Warming-induced thawing of peatland permafrost has been predicted to turn boreal and tundra biomes into carbon sources extraordinaire. According to this climate-alarmist contention, the exposure and subsequent decay of vast stores of newly-thawed organic matter will release massive amounts of long-sequestered carbon to the atmosphere as CO2 and methane, possibly freeing enough of the two trace gases at sufficiently rapid rates to rival more direct anthropogenic emissions. The end result of this scenario, in their view, is a tremendous positive feedback to the warming believed to be caused by the ongoing rise in the air's CO2 and methane concentrations, which they say will lead to even more serious global warming.

What was done
In a study germane to this scenario, Froese et al. investigated relict ground ice within the discontinuous permafrost zone of Canada's central Yukon Territory, where they found large vertically foliated ice wedges within a few meters of the surface that were overlain by a volcanic ash layer (Gold Run tephra), the age of which they determined by means of isothermal plateau glass fission-track and diameter-corrected glass fission-track methods, which are described in the Encyclopedia of Quaternary Science (Elsevier, Amsterdam, 2006).

What was learned
The researchers' measurements provided, in their words, "a weighted-mean age of 740,000 60,000 years before present," which they indicate is consistent with "faunal ages associated with this bed and the normal magnetic polarity of the surrounding sediments."

What it means
Froese et al. say their observations indicate that "permafrost has survived within the discontinuous permafrost zone since at least the early-Middle Pleistocene," noting that "this age range includes several glacial-interglacial cycles ... considered to be longer and warmer than the present interglaication." Most important of all, therefore, they say their finding "highlights the resilience of permafrost to past warmer climate and suggests that permafrost and associated carbon reservoirs that are more than a few meters below the surface may be more stable than previously thought," taking much of the wind out of the sails of those who claim these carbon stores will soon be released to the atmosphere in consequence of what they call the unprecedented warming of the late 20th century and its projected continuation over the remainder of the current century.

Reviewed 31 December 2008