Ecosystem and Soil Respiration Radiocarbon Detects Old Carbon Release as a Fingerprint of Permafrost Destabilization with Climate Change


Edward (Ted) A. G. Schuur1* ([email protected]), Caitlin Hicks Pries2, Marguerite Mauritz3, Elaine Pegoraro4, Heidi Rodenhizer5, Craig See1, Chris Ebert1


1Center for Ecosystem Science and Society and Department of Biological Sciences, Northern Arizona University–Flagstaff, AZ; 2Dartmouth College, Hanover, NH; 3Department of Biological Sciences, University of Texas–El Paso, TX; 4Lawrence Berkeley National Laboratory, Berkeley, CA; 5Woodwell Climate Research Center, Woods Hole, MA



Permafrost has accumulated organic carbon in cold and waterlogged soils over thousands of years and now contains three times as much carbon as the atmosphere. Global warming is degrading permafrost with the potential to accelerate climate change as increased microbial decomposition releases soil carbon as greenhouse gases. A 19-year time series of soil and ecosystem respiration radiocarbon from Alaska provides long-term insight into changing permafrost carbon dynamics in a warmer world. Nine percent of ecosystem respiration and 23% of soil respiration observations had radiocarbon values more than 50‰ lower than the atmospheric value. Furthermore, the overall trend of ecosystem and soil respiration radiocarbon values through time decreased more than atmospheric radiocarbon values did, indicating that old carbon degradation was enhanced. Boosted regression tree analyses showed that temperature and moisture environmental variables had the largest relative influence on lower radiocarbon values. This suggested that old carbon degradation was controlled by permafrost thaw and soil drying together, as waterlogged soil conditions could protect soil carbon from microbial decomposition even when thawed. Overall, changing conditions increasingly favored the release of old carbon, which is a definitive fingerprint of an accelerating feedback to climate change as a consequence of permafrost destabilization.