Proceedings of the 11th International Carbon Dioxide Conference

Permafrost soils located in high latitudes contain about 1500 petagrams of carbon. The strong and rapid warming of the Arctic climate threatens this important carbon stock. Permafrost thaw exposes previously frozen organic matter to decomposition by microorganisms, resulting in CO2 and CH4 emissions into the atmosphere that contribute to strengthening the initial warming. In addition, newly unfrozen nitrogen is likely to boost vegetation productivity in the same time. On the other hand, rising atmospheric CO2 concentration increases vegetation primary productivity in a feedback known as fertilization effect. The balance between these competing processes is thought to be the primary driver of future permafrost carbon stocks. However, both the amplitude and timing of future net carbon emissions of permafrost areas remain highly uncertain. Reducing the uncertainty on net carbon balance in high latitudes would help improve the accuracy of carbon budget, and thus would impact political and social decisions towards the net zero target. Up to then, different future scenarios have been explored with offline Land Surface Models but feedbacks with the atmosphere and ocean cannot be represented in such configurations. Using the IPSL Earth System Model that couples the atmosphere, the ocean and continental surfaces, the future evolution of climate-carbon feedbacks in permafrost regions is assessed. This model has been recently improved to include physical permafrost processes (soil freezing and insulation by soil organic carbon and non-vascular vegetation). In particular, we will estimate permafrost carbon emissions under different future IPCC scenarios and separate the effects of CO2 fertilization, nitrogen boost and climate on the permafrost carbon cycle. We show that the interactions between permafrost and nitrogen cycle challenge the established climate-carbon feedback in high latitudes.