The bitterly cold Arctic winter typically snuffs out the seasonal wildfires that erupt in this region. But every once in a while, a wildfire comes along that refuses to die.

These blazes, known as “zombie fires” or “holdover fires,” can burrow into the rich organic material beneath the surface, such as the vast peatlands that ring the Arctic, and smolder under the snowpack throughout the frigid winter.

With the Siberian Arctic seeing record warm conditions in recent weeks and months, scientists monitoring Arctic wildfire trends are becoming more convinced that some of the blazes erupting in the Arctic this spring are actually leftover from last summer.

Last year brought a record surge in fires to a region that is warming at more than twice the rate of the rest of the world. The Arctic contains vast stores of carbon and other planet-warming greenhouse gases in its soils, in peat as well as frozen soil is known as permafrost, that can be freed up through combustion. Peatlands are wetlands that contain ancient, decomposed and partially decomposed organic matter.

According to Mark Parrington, senior scientist and wildfire expert at the European Union’s Copernicus Atmosphere Monitoring Service (CAMS), recent Arctic fire detections have been found in areas where blazes were burning last summer, which lines up with regions affected by warmer-than-average and unusually dry surface conditions.

“We know from the climate data provided by C3S that the Arctic Circle regions most affected by fires in 2019 were experiencing warmer and drier surface conditions, providing the ideal environment for fires to burn and persist,” Parrington said in a news release, referring to the Copernicus Climate Change Service.

Scientists such as Parrington use satellite sensors to detect hot spots that could indicate wildfire activity.