Permafrost carbon as a missing link to explain CO2 changes during the last deglaciation

• Published in: Nature Geoscience
• Main Authors: CRICHTON, Katherine, BOUTTES, Nathaelle, ROCHE, Didier M., CHAPPELLAZ, Jerome, KRINNER, Gerhard
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2016
• Subjects: Carbon cycle; Climate change; Cryospheric science; Palaeoceanography; Palaeoclimate; Sciences de l'environnement; Ice; ice core; Ice Sheet; North Atlantic; permafrost
• Online Access: https://oskar-bordeaux.fr/handle/20.500.12278/199261; https://hdl.handle.net/20.500.12278/199261; https://doi.org/10.1038/ngeo2793

The atmospheric concentration of CO2 increased from 190 to 280 ppm between the last glacial maximum 21,000 years ago and the pre-industrial era1, 2. This CO2 rise and its timing have been linked to changes in the Earth’s orbit, ice sheet configuration and volume, and ocean carbon storage2, 3. The ice-core record of δ13CO2 (refs 2,4) in the atmosphere can help to constrain the source of carbon, but previous modelling studies have failed to capture the evolution of δ13CO2 over this period5. Here we show that simulations of the last deglaciation that include a permafrost carbon component can reproduce the ice core records between 21,000 and 10,000 years ago. We suggest that thawing permafrost, due to increasing summer insolation in the northern hemisphere, is the main source of CO2 rise between 17,500 and 15,000 years ago, a period sometimes referred to as the Mystery Interval6. Together with a fresh water release into the North Atlantic, much of the CO2 variability associated with the Bølling-Allerod/Younger Dryas period ~15,000 to ~12,000 years ago can also be explained. In simulations of future warming we find that the permafrost carbon feedback increases global mean temperature by 10–40% relative to simulations without this feedback, with the magnitude of the increase dependent on the evolution of anthropogenic carbon emissions.