Negative AMOC tipping feedback on permafrost carbon in climate mitigation scenarios

Recently, Wunderling et al., (2024) reviewed the current knowledge on climate tipping interactions and cascades, which highlighted lacking knowledge on the interaction between the AMOC and northern high-latitude permafrost carbon loss – labeled with ‘very limited/missing evidence’ for their interaction strength and direction. Here, we investigate the response of permafrost-carbon to idealized climate stabilization and overshoot scenarios with different modeling approaches ranging from complex to simplified Earth system models (ESM, LSM and SCM). Net warming in these mitigation scenarios results in irreversible loss of soil carbon from permafrost regions, even after achieving net-zero emissions. However, Northern Hemisphere regional cooling from a temporary slowdown or collapse of the AMOC partially negates the release of permafrost carbon. Our modeling approach allows for the first time to illustrate and quantify a stabilizing negative feedback loop between the AMOC and permafrost, whose effectiveness ranges between 30-60% of permafrost carbon loss reduction if the critical temperature for AMOC tipping is crossed.

[Wunderling, N., von der Heydt, A. S., Aksenov, Y., Barker, S., Bastiaansen, R., Brovkin, V., Brunetti, M., Couplet, V., Kleinen, T., Lear, C. H., Lohmann, J., Roman-Cuesta, R. M., Sinet, S., Swingedouw, D., Winkelmann, R., Anand, P., Barichivich, J., Bathiany, S., Baudena, M., Bruun, J. T., Chiessi, C. M., Coxall, H. K., Docquier, D., Donges, J. F., Falkena, S. K. J., Klose, A. K., Obura, D., Rocha, J., Rynders, S., Steinert, N. J., and Willeit, M.: Climate tipping point interactions and cascades: a review, Earth Syst. Dynam., 15, 41–74, https://doi.org/10.5194/esd-15-41-2024, 2024.]