Global warming-induced thawing of subarctic permafrost has been predicted to turn boreal and tundra biomes into carbon sources extraordinaire. According to this climate-alarmist hypothesis, the exposure and subsequent decay of vast stores of newly-thawed organic matter will release long-sequestered carbon back to the atmosphere as CO2, possibly freeing enough carbon at a sufficiently rapid rate to rival more direct emissions from anthropogenic sources. The end result of this scenario is envisioned to be a strong positive feedback to the ongoing rise in the air's CO2 content, which climate alarmists claim will lead to even more serious global warming. But is this contention correct?
In broaching this question, Payette et al. (2004) quantified the main patterns of change in a subarctic peatland on the eastern coast of Canada's Hudson Bay -- which was caused by permafrost decay between 1957 and 2003 -- via detailed surveys conducted in 1973, 1983, 1993 and 2003. This work revealed there was continuous permafrost thawing throughout the period of observation, with only 13% of the original frozen surface still remaining in 2003. This process, however, led to the establishment of fen/bog vegetation, which nearly always results in either no net loss of carbon or actual carbon sequestration. As a result, Payette et al. concluded that "contrary to current expectations, the melting of permafrost caused by recent climate change does not transform the peatland to a carbon-source ecosystem." Instead, they found that "rapid terrestrialization exacerbates carbon-sink conditions and tends to balance the local carbon budget."
In another pertinent study, Turetsky et al. (2007) explored "the influence of differing permafrost regimes (bogs with no surface permafrost, localized permafrost features with surface permafrost, and internal lawns representing areas of permafrost degradation) on rates of peat accumulation at the southernmost limit of permafrost in continental Canada" via a variety of techniques. In doing so, they found that "surface permafrost inhibits peat accumulation and that degradation of surface permafrost stimulates net carbon storage in peatlands." In fact, they report that "unfrozen bogs and internal lawns had net organic matter accumulation rates two-times faster [our italics] than rates of accumulation in localized permafrost features over the most recent 25-year horizon," a period when climate alarmists claim the planet warmed at a rate that was unprecedented over the past one to two millennia. As a result, the five researchers conclude that "permafrost degradation within peatland environments, likely triggered by climate change, could serve as a negative [our italics] feedback to net radiative forcing via enhanced [our italics] carbon accumulation as peat."
In light of these compelling observations, it would appear that even if global warming were to accelerate and reach a tipping point that led to the demise of much of the world's permafrost, the subsequent "terrestrialization" of these regions would actually lead to more carbon being stored in the soils and vegetation of these parts of the world, rather than -- as climate alarmist claim -- more being lost.
Payette, S., Delwaide, A., Caccianiga, M. and Beauchemin, M. 2004. Accelerated thawing of subarctic peatland permafrost over the last 50 years. Geophysical Research Letters 31: 10.1029/2004GL020358.
Turetsky, M.R., Wieder, R.K., Vitt, D.H., Evans, R.J. and Scott, K.D. 2007. The disappearance of relict permafrost in boreal North America: Effects on peatland carbon storage and fluxes. Global Change Biology 13: 1922-1934.Last updated 18 February 2009