Hysteresis of Northern Hemisphere permafrost to carbon dioxide emissions

• Published in: Environmental Research Letters
• Main Authors: Wei, Ting, Chen, Yueli, Wang, Hui
• Other Authors: National Natural Science Foundation of China, Basic Research Fund of CAMS
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: IOP Publishing 2024
• Subjects: Global warming; permafrost
• Online Access: http://dx.doi.org/10.1088/1748-9326/ad69a6; https://iopscience.iop.org/article/10.1088/1748-9326/ad69a6; https://iopscience.iop.org/article/10.1088/1748-9326/ad69a6/pdf

Abstract Carbon dioxide removal (CDR) is proposed to limit the level of global warming and minimize the impacts of climate crises. However, how permafrost may respond to negative carbon emissions remains unknown. Here, the response of near-surface permafrost in the Northern Hemisphere is investigated based on idealized carbon dioxide (CO 2 ) ramp-up (284.7–1138.8 ppm) and symmetric ramp-down model experiments. The results demonstrate that the timing of the minimum permafrost area lags the maximum CO 2 concentration for decades, which is also observed in soil temperatures at different depths and active layer thicknesses (ALTs). When the CO 2 concentration is reversed to the preindustrial level, the permafrost area decreases by ∼12% relative to the initial conditions, together with additional warming in the ground temperature at the top of the permafrost, indicating the hysteresis of permafrost to CO 2 removal. The most profound hysteretic responses occur at high latitudes for soil temperatures owing to Arctic amplification and at the southern margins of the permafrost zones for permafrost and ALT that largely linked to the climate state. Moreover, the sensitivity of permafrost and the associated thermodynamic factors to CO 2 change is generally lower during the CO 2 ramp-down phase than during the ramp-up phase, likely due to the release of stored heat on land. The results reveal the behaviour of permafrost in response to negative carbon emissions, which is informative for the projections of permafrost towards carbon neutral targets. In addition, the results may provide a reference for permafrost-related tipping points (e.g. releasing long-term stored greenhouse gases and destabilising recalcitrant soil carbon) and risk management in the future.