Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4 by A. V. Reyes & C. A. Cooke, PNAS,

Proceedings of the National Academy of Sciences, 108(12) (2011); doi:10.1073/pnas.1013270108

Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH₄

1. Alberto V. Reyes¹,²,³ and 
2. Colin A. Cooke¹,²,⁴

Abstract

Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (¹⁴C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality ¹⁴C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal ¹⁴C dates from Alaska as a case study, we show that nearly half the ¹⁴C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated ¹⁴C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated ¹⁴C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH₄ concentration at the start of the Bølling–Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH₄. Our results demonstrate that subtle methodological changes in the synthesis of basal ¹⁴C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle.

Link:  http://www.pnas.org/content/108/12/4748.abstract