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Long-term Carbon Accumulation Rates of Two Alaska Peatlands

Paper Reviewed
Taylor, L.S., Swindles, G.T., Morris, P.J., Galka, M. and Green, S.M. 2019. Evidence for ecosystem state shifts in Alaskan continuous permafrost peatlands in response to recent warming. Quaternary Science Reviews 207: 134-144.

Introducing their paper, Taylor et al. (2019) write that "land surface models suggest that the Arctic will become a net carbon source by the mid-2020s as a direct result of the degradation of permafrost and subsequent release of carbon," citing the work of Schaefer et al. (2011). 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 Taylor et al. reconstructed changes in two peatlands in separate watersheds within the continuous permafrost zone on Alaska's North Slope that were approximately 250 m apart and separated by a bedrock high. The paleoenvironmental reconstruction utilized testate amoeba to infer changes in water-table depth and porewater electrical conductivity, ultimately allowing the researchers to examine Holocene hydrological change and calculate peatland carbon accumulation rates since 0 A.D in one site and since 800 A.D. in the other.

Results indicated that prior to the modern rise in atmospheric CO2 and temperature (pre-1850) both peatlands had very low carbon accumulation rates reflecting the slow formation of peat. However, since 1850 there has occurred what the authors describe as "a rapid transition towards oligotrophy and a three-fold increase in mean carbon accumulation rate." Specifically, mean carbon accumulation rates at the two sites were a meager 18.4 and 14.2 g C m-2 yr-1 before 1850, but rose to mean rates of 59.5 and 48.2 g C m-2 yr-1 over the past 170 years.

The greatly enhanced sequestration of carbon by the peatlands in modern times was attributed by the authors to the recent warming observed since the end of the Little Ice Age, leading them to conclude "our work demonstrates that some Arctic peatlands may become more productive with future regional warming, subsequently increasing their ability to sequester carbon," adding that "as the Arctic continues to warm, peatlands in the continuous permafrost zone may become an increasingly important carbon sink." And this latter conclusion is a far cry from the model projections cited by the authors of the Arctic becoming a net carbon source by the mid-2020s!

Schaefer, K., Zhang, T., Bruhwiler, L. and Barrett, A.P. 2011. Amount and timing of permafrost carbon release in response to climate warming. Tellus 63: 165e180.

Posted 19 June 2020