06/13/2016

Thawing Permafrost Could Accelerate Carbon Releases to the Atmosphere

Carbon dioxide, rather than methane, found to dominate potential greenhouse gas emissions.

The Science

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 (CO₂) or methane (CH₄), a more potent greenhouse gas.

The Impact

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.

Summary

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?

Principal Investigator(s)

Colleen M. Iversen Colleen M. Iversen
Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory
[email protected]

Funding

Financial support was provided by the National Science Foundation (NSF) Vulnerability of Permafrost Carbon Research Coordination Network grant 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 1331083. Additional funding came from the 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.; United Kingdom Natural Environment Research Council (NE/K000179/1); German Research Foundation (Excellence cluster CliSAP); Department of Ecosystem Biology, Grant agency of South Bohemian University, GAJU project numbers 146/2013/P and 146/2013/D; NSF Office of Polar Programs (1312402); NSF Division of Environmental Biology (0423385 and 1026843); European Union (FP-7-ENV-2011, project PAGE21, contract number 282700); Academy of Finland (project CryoN, decision number 132 045); Academy of Finland (project COUP, decision number 291691; part of the European Union Joint Programming Initiative, Climate); University of Eastern Finland (project FiWER); Maj and Tor Nessling Foundation; and Nordic Center of Excellence (project DeFROST).

References

Schädel C, Bader MKF, Schuur EAG, Biasi C, Bracho R, Capek P, De Baets S, Diakova K, Ernakovich J, Estop-Aragones C, Graham DE, Hartley IP, Iversen CM, Kane E, Knoblauch C, Lupascu M, Martikainen PJ, Natali SM, Norby RJ, O’Donnell JA, Chowdhury TR, Santruckova H, Shaver G, Sloan VL, Treat CC, Turetsky MR, Waldrop MP, Wickland KP. “Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils.” Nature Climate Change 6, 950–953 (2016). [DOI:10.1038/nclimate3054]