Sudden worsening of forest fires in the north due to future thawing of permafrost

Current observational trends suggest that warm and unusually dry conditions have already increased wildfires in the Arctic. To understand and simulate how future human-induced warming will affect wildfire occurrence, it is important to consider the role of accelerated permafrost thawing, as this strongly influences soil water content – a key factor in wildfires. Current climate models have not fully accounted for the interaction between global warming, permafrost thawing in high northern latitudes, soil water, and fires.

The new study uses data on permafrost and wildfires generated by one of the most comprehensive Earth system models – the Community Earth System Model. It is the first model of its kind to capture the coupling between soil water, permafrost and wildfires in an integrated way. To better separate the anthropogenic effect of increasing greenhouse gas emissions from naturally occurring climate variability, the scientists used an ensemble of 50 past-future simulations for the period 1850-2100 AD (SSP3-7.0 greenhouse gas emission scenario) recently performed by scientists from the IBS Center for Climate Physics, Busan (South Korea) and the National Center for Atmospheric Research in Boulder, Colorado (USA) on the IBS supercomputer Aleph.

Using this ensemble modeling approach, the team showed that by the mid- to late 21st century,^st Human-induced permafrost thawing in the subarctic and arctic regions during the 20th century will be very extensive. In many areas, excess soil water can drain away quickly, causing a sudden drop in soil moisture, subsequent surface warming and drying of the atmosphere. “These conditions will increase wildfires,” says Dr. In-Won Kim, lead author of the study and postdoctoral fellow at the IBS Center for Climate Physics in Busan, South Korea. “In the second half of this century, our model simulations show an abrupt change from virtually no fires to very intense fires within a few years,” she adds.

These future trends are further exacerbated by the fact that vegetation biomass in high-latitude areas is likely to increase due to rising CO2 concentrations in the atmosphere.₂ concentrations. This so-called CO₂ The fertilizing effect thus provides additional fuel.

“To better simulate future degradation of the complex permafrost landscape, it is necessary to further improve small-scale hydrological processes in Earth system models using expanded observational data sets,” says Associate Prof. Hanna Lee, co-author of the study at the Norwegian University of Science and Technology in Trondheim, Norway.

“Forest fires release carbon dioxide as well as black and organic carbon into the atmosphere, which can affect the climate and lead to the thawing processes of permafrost in the Arctic. However, the interactions between fire emissions and atmospheric processes are not yet fully integrated into computer models of the Earth system. Further consideration of this aspect would be the next step,” says Prof. Axel Timmermann, co-author of the study and Director of the ICCP and Distinguished Professor at Pusan ​​​​National University.