“Especially because of the carbon, permafrost is a particular focus of climate research. In this regard, numerous studies offer a scientifically sound picture of the status quo,” says Jens Strauss, first author of the study and head of the Permafrost Biogeochemistry working group at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “In contrast, we have very few data on the amount of nitrogen stored in the soil, which is also highly relevant for the climate. Our study is the first to determine just how much nitrogen the permafrost actually contains down to considerable depths.”
The international team, consisting of researchers from Germany, Finland, the US, Canada and China focussed on Yedoma permafrost, a type of permafrost that is predominantly found in eastern Siberia and Alaska. Because of its high ice content, Yedoma is considered to be especially climate-sensitive. When it warms, it can collapse and rapidly thaw to depths of several metres. As a result, it can activate significantly more organic material than other types of permafrost. In the course of the study, Jens Strauss and his team analysed more than 2,200 soil samples from Siberia and Alaska, determined the nitrogen concentration, and subsequently calculated the size of the total pool.
“According to our findings, the Yedoma region contains 41.2 metric gigatons of nitrogen. As such, the reservoir is considerably larger than indicated by previous estimates,” Strauss explains. “Of those 41.2 gigatons, 37 gigatons – or roughly 90 percent – are still frozen and not bioavailable. But this will change as climate change continues. Based on our calculations, in a future scenario with continuing high anthropogenic greenhouse-gas emissions, between 4 and 16 gigatons of nitrogen could be thawed and activated in Yedoma by the year 2100.”
The consequences of this surprisingly high amount for the climate chiefly depend on the microorganisms in the soil. “The newly bioavailable nitrogen could promote plant growth, since plants need nitrogen. And if the plants could access this nitrogen, they could absorb CO2 from the atmosphere, which means the effect on the climate would be positive for a certain time,” says Strauss. “But this microbial decomposition could also release large amounts of N2O into the atmosphere. This nitrous oxide – better known as laughing gas – is also a greenhouse gas 300 times as potent as CO2, which means it can seriously affect the climate. That’s why we’ll need further studies to determine just what will happen to this newly activated nitrogen pool.”
Jens Strauss, Christina Biasi, Tina Sanders, Benjamin W. Abbott, Thomas Schneider von Deimling, Carolina Voigt, Matthias Winkel, Maija E. Marushchak, Dan Kou, Matthias Fuchs, Marcus A. Horn, Loeka L. Jongejans, Susanne Liebner, Jan Nitzbon, Lutz Schirrmeister, Katey Walter Anthony, Yuanhe Yang, Sebastian Zubrzycki, Sebastian Laboor, Claire Treat and Guido Grosse: A globally relevant stock of soil nitrogen in the Yedoma permafrost domain. Nature Communications (2022). DOI: https://www.doi.org/10.1038/s41467-022-33794-9