An international team of permafrost scientists has summarized the status quo about the risk of thawing permafrost. The study was released in the journal Nature. “When the soil thaws, microorganisms and bacteria start to desintegrate the organic matter that has been locked inside the earth for millennia, producing carbon dioxide and methane. Therefore, if the global mean temperature continues to rise, permafrost could release more greenhouse gases”, says Dr. Guido Grosse, permafrost scientist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) and co-author of the current study. “If you consider that permafrost regions, which make up nearly a quarter of the land surface area in the Northern Hemisphere, will likely release just as much greenhouse gas as the man-made changes in land use, you begin to realise just how important these processes are for our climate”, Grosse adds.
The carbon content of the three top meters in permafrost regions can be limited to about 1.035 billion tons. However, there are more carbon deposits in deeper layers. The authors of the permafrost carbon network estimate the known stored soil carbon stock in the permafrost up to 1.330-1.580 billion tons. Further, there is a considerable and still unmeasured amount hidden underwater in the shelf seas of the Arctic coasts, where submarine permafrost occurs.
The team of scientists believes that the permafrost will thaw gradually and continuously. This process is very difficult to stop even if industrial greenhouse gas emissions will be drastically reduced. Especially in areas with a lot of ice in Alaska, Siberia and Canada the thawing process can occur very quickly as so called thermokarst lakes cause thawing of sediment layers also in great depths. “As such, we consider these thermokarst processes to be a clear sign that the thawing isn’t always gradual, but instead that under certain conditions – like intense warming or altered precipitation levels – can be quite sudden at the regional level,” explains Dr. Guido Grosse.
Nevertheless, 15 percent of the readily transformable carbon could be released as greenhouse gases by the year 2100. This would contribute to further global warming of up to 0.27 degrees Celsius by the end of this century. The context of carbon release from permafrost to climate warming is so far not included in climate models of the IPCC (Intergovernmental Panel on Climate Change).
The AWI is working on international projects (GTN-P and PAGE21) to establish permafrost records as essential climate variables and add them in global models. A possible result could be more critical predictions of temperature trends for the 21st century.
Literature/Sources: Schuur, E. A. G., McGuire, A. D., Schadel, C., Grosse, G., Harden, J. W., Hayes, D. J., Hugelius, G., Koven, C. D., Kuhry, P., Lawrence, D. M., Natali, S. M., Olefeldt, D., Romanovsky, V. E., Schaefer, K., Turetsky, M. R., Treat, C. C., and Vonk, J. E.: Climate change and the permafrost carbon feedback, Nature, 520, 171-179, 2015.
