Why the Arctic will literally explode

Unrelenting 21st century climate change will accelerate arctic and subarctic thawing of permafrost, which may intensify microbial degradation of carbon-rich soil, methane emissions, and global warming. The impact of melting permafrost on future arctic and subarctic fires and the associated release of greenhouse gases and aerosols is less well understood. Here, we present a comprehensive analysis of the impact of future permafrost thaw on land surface processes in the arctic-subarctic region using the large CESM2 ensemble forced by the SSP3-7.0 greenhouse gas emissions scenario. By analyzing 50 greenhouse warming simulations that capture the coupling between permafrost, hydrology, and the atmosphere, we found that predicted rapid permafrost melting leads to massive soil drying, surface warming, and reduced relative humidity in the arctic-subarctic region. These combined processes lead to late 21st century nonlinear regime shifts in the coupled soil-hydrological system and rapid fire intensification in western Siberia and Canada. (In-Won Kim, Axel Timmermann, William R. Wieder, more at nature.com)