Mapping potential carbon emissions from thawing permafrost
A new global mapping project has for the first time assessed thermokarst landscapes in the northern circumpolar region, concluding that as much as half of the carbon below-ground and at risk of being released into the atmosphere lies in these unique landforms. The results were published in Nature Communications on October 11.
Thermokarst forms when ice-rich permafrost ground thaws and causes land subsidence. The mapping project, led by the University of Alberta and the Climate Change Science Institute (CCSI) at Oak Ridge National Laboratory, estimates that these landforms cover about 20% of the northern permafrost.
Scientists can now look to these areas to test assumptions about how fast soil organic matter will release greenhouse gases. For instance, the researchers noted that rapid carbon loss in many thermokarst landforms is likely due to increased microbial access to soil organic carbon, given that soil thawed through thermokarst processes often remains unfrozen all year round.
Current estimates indicate that greenhouse gas emissions from thawing permafrost soils could be a contributor to climate change on the same scale as global deforestation, the researchers said.
Coauthors Santonu Goswami of the Indian Space Research Organization was a postdoctoral researcher in the CCSI and the Energy and Environmental Sciences Directorate at the time of the study, while Daniel Hayes of the University of Maine School of Forest Resources was also a CCSI researcher. They carried out the geographic information system aspects of the mapping project and helped developed the framework for estimating thermokarst landscape distribution.
To produce the map, the researchers linked thermokarst occurrence to certain landscape characteristics for which information exists. By layering available maps of topography, soil type, and permafrost conditions, they created a new map that shows which regions are good candidates for having lots of thermokarst landforms.
The map will advance the study of the broad impacts of accelerated thermokarst in areas such as soil carbon cycling, greenhouse gas exchange with the atmosphere, infrastructure, landscape ecology, surface water quality, and catchment hydrology.
David Olefeldt of the University of Alberta’s Department of Renewable Resources was the project lead. Other participants were Guido Grosse of the Alfred Wegener Institute for Polar and Marine Research, Gustaf Hugelius, Peter Kuhry, and A. Britta K. Sannel of Stockholm University, A. David McGuire of the US Geological Survey, Vladimir E. Romanovsky of the University of Alaska-Fairbanks, Ted Schuur of Northern Arizona University, and Merritt Turetsky of the University of Guelph, Ontario.
The thermokarst landscape map is available on the ORNL DAAC website at: https://daac.ornl.gov/SOILS/guides/Thermokarst_Circumpolar_Map.html
The paper is available online at: http://www.nature.com/articles/ncomms13043
By Stephanie Seay