Vulnerability of permafrost carbon: Results from a research coordination network survey

Background/Question/Methods

Approximately 1700 Pg of soil carbon are stored in the northern circumpolar permafrost zone, more than twice as much carbon than currently contained in the atmosphere.  Permafrost thaw, and the microbial decomposition of previously frozen organic carbon, is considered one of the likely positive feedbacks from terrestrial ecosystems to the atmosphere in a warmer world.  Yet, the rate and form of release is highly uncertain but crucial for predicting the strength and timing of this carbon cycle feedback this century and beyond.  Here we report on the formation of a new research coordination network (RCN) whose objective is to link biological C cycle research with networks focused on the thermal state of permafrost. We found that published literature in the SCI identified with the search terms ‘permafrost’ and ‘carbon’ have increased dramatically in the last decade. Of total publications including those keywords, 86% were published since 2000, 65% since 2005, and 36% since 2008.  Interconnection through this RCN is designed to produce new knowledge through research synthesis that can be used to quantify the role of permafrost carbon in driving climate change. 

Results/Conclusions

An expert elicitation revealed that the total effect of carbon release from permafrost zone soils on climate is expected to be up to 24-58 Pg C over the next three decades, reaching 208-377 Pg C by 2100 and potentially up to 482-812 Pg C over the next several centuries under the strongest warming scenario presented to the group. These values, expressed in billions of tons of C in CO₂ equivalents, combine the effect of C released both as CO₂ and as CH₄ by accounting for the greater heat-trapping capacity of CH₄ over a twenty-year time horizon. Much of the actual C release by weight is expected to be in the form of CO₂, with only about 2.3% of that in the form of CH₄. However, the higher global warming potential of CH₄ means that up to half of the effect of future permafrost zone carbon emissions on climate forcing was expected by this group to be a result of CH₄ emissions from wetlands, lakes, and other oxygen-limited environments.  These results demonstrate the vulnerability of organic C stored in near surface permafrost to increasing temperatures.  Future activities of this network include synthesizing information in formats that can be assimilated by biospheric and climate models, and that will contribute to future assessments of the IPCC.