Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw


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claire.treat [ at ] awi.de

Abstract

Northern peatlands have accumulated large stocks of organic carbon (C) and nitrogen (N), but their spatial distribution and vulnerability to climate warming remain uncertain. Here, we used machine-learning techniques with extensive peat core data (n > 7,000) to create observation-based maps of northern peatland C and N stocks, and to assess their response to warming and permafrost thaw. We estimate that northern peatlands cover 3.7 ± 0.5 million km2 and store 415 ± 150 Pg C and 10 ± 7 Pg N. Nearly half of the peatland area and peat C stocks are permafrost affected. Using modeled global warming stabilization scenarios (from 1.5 to 6 °C warming), we project that the current sink of atmospheric C (0.10 ± 0.02 Pg C⋅y−1) in northern peatlands will shift to a C source as 0.8 to 1.9 million km2 of permafrost-affected peatlands thaw. The projected thaw would cause peatland greenhouse gas emissions equal to ∼1% of anthropogenic radiative forcing in this century. The main forcing is from methane emissions (0.7 to 3 Pg cumulative CH4-C) with smaller carbon dioxide forcing (1 to 2 Pg CO2-C) and minor nitrous oxide losses. We project that initial CO2-C losses reverse after ∼200 y, as warming strengthens peatland C-sinks. We project substantial, but highly uncertain, additional losses of peat into fluvial systems of 10 to 30 Pg C and 0.4 to 0.9 Pg N. The combined gaseous and fluvial peatland C loss estimated here adds 30 to 50% onto previous estimates of permafrost-thaw C losses, with southern permafrost regions being the most vulnerable.



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Eprint ID
52941
DOI 10.1073/pnas.1916387117

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Hugelius, G. , Loisel, J. , Chadburn, S. , Jackson, R. B. , Jones, M. , MacDonald, G. , Marushchak, M. , Olefeldt, D. , Packalen, M. , Siewert, M. B. , Treat, C. , Turetsky, M. , Voigt, C. and Yu, Z. (2020): Large stocks of peatland carbon and nitrogen are vulnerable to permafrost thaw , Proceedings of the National Academy of Sciences, 117 (34), pp. 20438-20446 . doi: 10.1073/pnas.1916387117


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info:eu-repo/grantAgreement/EC/H2020/773421


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