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Cryoturbation Effects on Soil Organic Matter in a Warming Arctic
Bockheim, J.G. 2007. Importance of cryoturbation in redistributing organic carbon in permafrost-affected soils. Soil Science Society of America Journal 71: 1335-1342.

The author writes that "cryoturbation is a dominant process in permafrost regions and refers collectively to all soil movements due to frost action," while reporting that several studies suggest cryoturbation "was particularly active during mid-Holocene warming periods in the arctic;" and from that observation comes the key question addressed in this paper: "what effect will sustained warming have on redistribution of soil organic carbon, and will this redistribution exacerbate or mitigate release of CO2 to the atmosphere?"

What was done
Bockheim's study examined the amount of soil organic carbon (SOC) incorporated by cryoturbation into the active layer and near-surface permafrost of 21 sites in northern Alaska, 10 of which are located in the Arctic Coastal Plain and 11 of which are in the Arctic Foothills.

What was learned
The University of Wisconsin researcher reports that the data acquired from the 21 sites reveal that "55% of the SOC density of the active layer and near-surface permafrost could be attributed to redistribution from cryoturbation," while listing "five lines of evidence suggesting that increased cryoturbation from arctic warming will result in increased storage of SOC." First, "once cryoturbation has moved SOC to the cold, deeper soil layers, little or no biological decomposition will take place." Second, "major organic horizons that are cryoturbated ... are 10 to 50% more dense than the equivalent uncryoturbated horizons," and "low-density SOC may be more susceptible to decomposition than high-density SOC." Third, "low-molecular-weight neutrally charged organic compounds are more biodegradable than high-molecular fractions." Fourth, "Kaiser et al. (2007) reported lower decomposition rates of redistributed SOC in Siberian subsoils than in equivalent material collected from the surface." And fifth, "mechanistic models (Waelbroeck et al., 1997) predict that sustained arctic warming will result in permafrost thawing and a delayed long-lasting increase in SOC storage."

What it means
In the concluding words of Bockheim, "these results suggest that continued warming of the arctic may accelerate cryoturbation," and that "this, in turn, will increase the incorporation of dense, high-molecular-weight SOC at depth, thereby enabling the soil to store more SOC than at present and reducing the loss of CO2 to the atmosphere from soil respiration," which is essentially just the opposite of what climate alarmists usually contend.

Kaiser, C., Meyer, H., Biasi, C., Rusalimova, O., Barsukov, P. and Richter, A. 2007. Conservation of soil organic matter through cryoturbation of arctic soils in Siberia. Journal of Geophysical Research 112: 10.1029/2006JG000258.

Waelbroeck, C.P., Monfray, W.C., Oechel, W.C., Hastings, S. and Vourlius, G. 1997. The impact of permafrost thawing on the carbon dynamics of tundra. Geophysical Research Letters 24: 229-232.

Reviewed 26 December 2007