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TitleLimited contribution of permafrost carbon to methane release from thawing peatlands
AuthorCooper, M D A; Estop-Aragones, C; Fisher, J P; Thierry, A; Garnett, M H; Charman, D J; Murton, J B; Phoenix, G K; Treharne, R; Kokelj, S V; Wolfe, S A; Lewkowicz, A G; Williams, M; Hartley, I P
SourceNature Climate Change vol. 7, no. 7, 2017 p. 507-511, https://doi.org/10.1038/NCLIMATE3328
Year2017
Alt SeriesEarth Sciences Sector, Contribution Series 20160276
PublisherNature Publishing Group
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; html
ProgramLand-based Infrastructure, Climate Change Geoscience
AbstractModels predict that thaw of permafrost soils at northern high latitudes will release tens of billions of tonnes of carbon (C) to the atmosphere by 2100 (refs 1-3). The effect on the Earth's climate depends strongly on the proportion of this C that is released as the more powerful greenhouse gas methane (CH4), rather than carbon dioxide (CO2) (refs 1,4); even if CH4 emissions represent just 2% of the C release, they would contribute approximately one-quarter of the climate forcing (ref 5). In northern peatlands, thaw of ice-rich permafrost causes surface subsidence (thermokarst) and water-logging(ref 6), exposing substantial stores (tens of kilograms of C per square meter, ref. 7) of previously frozen organic matter to anaerobic conditions, and generating ideal conditions for permafrost-derived CH4 release. Here we show that, contrary to expectations, although substantial CH4 fluxes (>20 g CH4 m(-2) yr(-1)) were recorded from thawing peatlands in northern Canada, only a small amount was derived from previously frozen C (<2 g CH4 m(-2) yr(-1)). Instead, fluxes were driven by anaerobic decomposition of recent C inputs. We conclude that thaw-induced changes in surface wetness and wetland area, rather than the anaerobic decomposition of previously frozen C, may determine the effect of permafrost thaw on CH4 emissions from northern peatlands.
Summary(Plain Language Summary, not published)
Climate models predict that thaw of permafrost soils at northern high-latitudes will release tens of billions of tonnes of carbon to the atmosphere by the end of the century. In northern peatlands, thaw of ice-rich permafrost causes surface subsidence and water-logging exposing previously-frozen organic matter to anaerobic conditions, and contributing to permafrost-derived methane release. Here we show that, contrary to expectations, only a small proportion of the substantial methane in thawing peatlands in northern Canada was derived from previously-frozen carbon. Instead, anaerobic decomposition of current carbon inputs drove these fluxes Our study also demonstrates that changes in hydrological conditions near the peat surface, promoting the anaerobic decomposition of new carbon inputs, will play the dominant role in controlling methane flux rates from thawing permafrost peatlands. This must be represented explicitly in model projections of the permafrost feedback.
GEOSCAN ID299446