Continued global warming is creating conditions that will likely cause dramatic increases in Arctic wildfires within the coming decades, potentially releasing massive stores of organic carbon from burned peatlands into the atmosphere, according to a new study. Using satellite data, Adrià Descals and colleagues show that the fires in the Siberian Arctic burned nearly 4.7 million hectares (Mha) in 2019 and 2020, which accounted for 44% of the total burned area in this region for almost the last 40 years. They argue that temperatures in the Arctic – one of the most rapidly warming regions on the planet – could be headed towards a threshold where small temperature increases could result in exponential increases in area burned. Arctic soils store vast amounts of organic carbon, much of which is in the form of peatlands. Although often frozen or waterlogged, climate warming thaws and dries peatland soils, increasing the likelihood of large Arctic wildfires. Burning of these carbon-rich soils releases this carbon into the atmosphere as carbon dioxide, fueling a feedback loop of continued warming, subsequent burning, and CO2 emission. Descals et al. used six satellite-derived maps to evaluate annual burned area in the Siberian Arctic for 1982-2020 and combined it with an analysis of 10 climatic factors associated with the likelihood of fires, including temperature and precipitation. They found that fires burned at the highest rates in 2019 and 2020 and accounted for 44% of all the total area burned across their nearly 40-year-long study period, releasing almost 150 million tons of carbon into the atmosphere. 2019 and 2020 were also the warmest years across the study. According to the authors, the findings suggest an exponential relationship between fire associated with increased temperature and annual burned area. The Siberian Arctic has already doubled the long-term average of burned area in just the last three years of their analysis. This could indicate a profound shift in the region's fire regimes caused by accelerating climatic warming. "Larger and more intense wildfires could substantially accelerate the release of permafrost carbon into the atmosphere, but this interaction is not considered in current forecasts of Arctic feedback to global warming," write Eric Post and Michelle Mack in a related Perspective. "Future studies that link rigorous assessment of wildfires with the dynamics of permafrost thaw in these remote regions are therefore needed to better quantify their climate impact."
For reporters interested in trends, another study in this issue also investigates recent extreme Siberian wildfire seasons. In this study, Rebecca Scholten and colleagues used data from the satellite-borne Moderate Resolution Imaging Spectroradiometer (MODIS) to evaluate fire activity in the Siberian Arctic between 2001 and 2021. Scholten et al. found that early snowmelt combined with an anomalous Arctic front jet over northeastern Siberia promoted unusually dry and warm surface conditions, which was followed by unusually high lightning and fire activity. They show that these interconnected climatic drivers have been increasing over the last several decades and are likely driving extreme fire activity in the region. These fires have the potential to accelerate the thawing and degradation of carbon-rich permafrost peatlands.
