Wildfires raging across Arctic and boreal regions are igniting ancient carbon in soils, releasing far more carbon dioxide than climate models have assumed. A new study of soil cores shows that some fires are burning organic matter up to 5,000 years old.
Meri Ruppel at the Finnish Meteorological Institute led the research. Her team collected soil cores from fire sites and found that surface vegetation burns often trigger slower smouldering in deeper, older layers. This process releases both carbon dioxide and black carbon that absorbs sunlight and accelerates melting when it lands on ice or snow.