July 20, 2016
Thawing Permafrost Could Accelerate Carbon Releases to the Atmosphere
Carbon dioxide, rather than methane, found to dominate potential greenhouse gas emissions.
Rapid warming in the Arctic is leading to the thawing of carbon-rich soils that have been permanently frozen for millennia. As these soils thaw, microbial decomposition could release greenhouse gases and increase the rate of global warming. A recent study looked at the potential amount of carbon that could be released into the atmosphere through this thawing and whether that carbon would be released as carbon dioxide or methane, a more potent greenhouse gas.
The Arctic study found that the total amount of carbon released from thawing soils, and whether the carbon was released as CO2 or CH4, was related to whether soils were drier and aerobic or waterlogged and anaerobic. Total carbon release, even when taking into account the stronger warming potential of CH4, was greatest under aerobic soil conditions, indicating that drier soils may provide a larger, positive feedback to global warming than wetter soils.
An international research team led by Northern Arizona University used two meta-analyses to investigate the greenhouse gas release from soils sampled from across the permafrost zone and warmed in laboratory incubations. The first analysis focused on the amount of carbon released in response to warming, while the second analysis focused on the difference in the relative amount of carbon released as CO2 or CH4 under aerobic or anaerobic soil conditions. Potential warming of 10°C increased total carbon release by a factor of two, and even when taking into account the stronger warming potential of CH4, total carbon release was greatest under aerobic soil conditions. The implications of these results are that drier soils may provide a larger, positive feedback to global warming than wetter soils. Further studies are focused on addressing some of the key questions raised by this research. For example, where, when, and why will the Arctic become wetter or drier, and what are the implications for climate forcing? How should these processes be represented by mechanistic models of the Arctic?
Colleen M. Iversen
Oak Ridge National Laboratory
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
Financial support was provided by the National Science Foundation (NSF) Vulnerability of Permafrost Carbon Research Coordination Network Grant no. 955713, with continued support from the NSF 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: Terrestrial Ecosystem Science (TES) program of the Office of Biological and Environmental Research (BER), within the U.S. Department of Energy (DOE) Office of Science (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.; NSF Office of Polar Programs (1312402) to S.M.N.; NSF Division of Environmental Biology (0423385) and Division of Environmental Biology (1026843), both to the Marine Biological Laboratory, Woods Hole, Massachusetts; additionally, the Next-Generation Ecosystem Experiments (NGEE)–Arctic project is supported by BER within the DOE Office of Science. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for 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).
Schädel, C., M. K. F. Bader, E. A. G. Schuur, and C. Blasi, et al.. "Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils". Nature Climate Change 6 950–953 (2016). https://doi.org/10.1038/nclimate3054.