The loss of ecosystem carbon (the sum of vegetation, litter, and soil carbon) may occur in permafrost region under mitigation pathways, which could reduce the efficiency of carbon dioxide removal. Here, we investigate changes in permafrost under net-zero and negative emissions, based on idealized emission-driven simulations using a state-of-the-art Earth system model. While acting as a net ecosystem carbon sink during the most of the positive emission phase, permafrost becomes a net ecosystem carbon source just before reaching net-zero and negative emissions. Permafrost slowly recovers, especially in regions with high organic carbon content, and net ecosystem carbon losspersists until the end of simulations, resulting in a cumulative net ecosystem carbon loss of approximately 14 PgC in both scenarios. In addition, methane emissions increase under net-zero and negative emissions, due to the irreversibility of the inundated areas. We conclude that the permafrost ecosystem carbon loss may continue under net-zero and negative emissions, which could hinder climate change mitigation efforts.

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