Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils

PublishedIncreasing temperatures in northern high latitudes are causing permafrost to thaw1, making large amounts of previously frozen organic matter vulnerable to microbial decomposition2. Permafrost thaw also creates a fragmented landscape of drier and wetter soil conditions3, 4 that determine the amount and form (carbon dioxide (CO2), or methane (CH4)) of carbon (C) released to the atmosphere. The rate and form of C release control the magnitude of the permafrost C feedback, so their relative contribution with a warming climate remains unclear5, 6. We quantified the effect of increasing temperature and changes from aerobic to anaerobic soil conditions using 25 soil incubation studies from the permafrost zone. Here we show, using two separate meta-analyses, that a 10 °C increase in incubation temperature increased C release by a factor of 2.0 (95% confidence interval (CI), 1.8 to 2.2). Under aerobic incubation conditions, soils released 3.4 (95% CI, 2.2 to 5.2) times more C than under anaerobic conditions. Even when accounting for the higher heat trapping capacity of CH4, soils released 2.3 (95% CI, 1.5 to 3.4) times more C under aerobic conditions. These results imply that permafrost ecosystems thawing under aerobic conditions and releasing CO2 will strengthen the permafrost C feedback more than waterlogged systems releasing CO2 and CH4 for a given amount of C.Financial support was provided by the National Science Foundation Vulnerability of Permafrost Carbon Research Coordination Network Grant no. 955713 with continued support from the National Science Foundation Research Synthesis, and Knowledge Transfer in a Changing Arctic: Science Support for the Study of Environmental Arctic Change Grant no. 1331083. Author contributions were also supported by grants to individuals: Department of Energy, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program (DE-SC0006982) to E.A.G.S.; UK Natural Environment Research Council funding to I.P.H. and C.E.-A. (NE/K000179/1); German Research Foundation (DFG, Excellence cluster CliSAP) to C.K.; Department of Ecosystem Biology, Grant agency of South Bohemian University, GAJU project no. 146/2013/P and GAJU project no. 146/2013/D to H.S.; National Science Foundation Office of Polar Programs (1312402) to S.M.N.; National Science Foundation Division of Environmental Biology (0423385) and National Science Foundation Division of Environmental Biology (1026843), both to the Marine Biological Laboratory, Woods Hole, Massachusetts; additionally, the Next-Generation Ecosystem Experiments in the Arctic (NGEE Arctic) project is supported by the Biological and Environmental Research programme in the US Department of Energy (DOE) Office of Science. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the DOE under Contract no. DE-AC05-00OR22725. Support for C.B. came from European Union (FP-7-ENV-2011, project PAGE21, contract no. 282700), Academy of Finland (project CryoN, decision no. 132 045), Academy of Finland (project COUP, decision no. 291691; part of the European Union Joint Programming Initiative, JPI Climate), strategic funding of the University of Eastern Finland (project FiWER) and Maj and Tor Nessling Foundation and for P.J.M. from Nordic Center of Excellence (project DeFROST)