Abstract
Fire activity in Arctic and boreal regions is rapidly increasing with severe consequences for climate and human health. Long-term variations in fire frequency and intensity within regions characterize fire regimes. The spatial variability in Arctic-boreal fire regimes and their climatic and anthropogenic drivers, however, remain poorly understood. Here, we developed an object-based fire tracking system to map the sub-daily evolution of all circumpolar Arctic-boreal fires between 2012 and 2023 using 375m Visible Infrared Imaging Radiometer Suite (VIIRS) active fire detections. This dataset characterizes the ignition time, location, size, duration, spread, and intensity of individual fires. We used the resulting fire atlas to classify the Arctic-boreal biomes into seven distinct pyroregions with unique climatic and geographic environments. The pyroregions exhibited varying responses to environmental drivers, with boreal North America, eastern Siberia, and northern tundra regions showing the highest sensitivity to climate and lightning density. Anthropogenic factors also played an important role in influencing fire number and size, interacting with other factors. Understanding the spatial variability of fire regimes and its interconnected drivers in the Arctic-boreal domain is important for improving future predictions of fire activity and identifying areas at risk for extreme events.