Analyzing Spatiotemporal Dynamics of Arctic Wildfires Using MODIS Data

The Arctic Fires Exploratory Study (AFES) aims to conduct an exploratory spatiotemporal analysis to reveal spatial patterns and temporal fluctuations of wildfire events in different parts of the Arctic. Tundra wildfires have an important impact on arctic ecosystems. Since tundra vegetation is very slow to recover, wildfires can substantially alter the amount of biomass and animal abundance in affected areas. Whereas boreal forest fires are well studied, the knowledge base about tundra wildfires is limited. Most arctic fires take place in remote areas and remain unmonitored from the ground or air. This study uses MODIS-derived active fire data to analyze spatial and temporal patterns of tundra wildfires between 2004 and 2008. The dataset incorporates locations of active fire events and estimates of fire radiated power (FRP).

On average there are 300–400 arctic fires registered by MODIS sensors every year. The largest number of fire events is recorded in 2005. The wildfires exhibit clear seasonality determined by seasonal changes in tundra landscapes with most fires occurring in July and August. We observed inter-year fluctuations when a fire season either started earlier (in June) or lasted longer (in to September). In terms of spatial distribution, the wildfires demonstrate a strong tendency to cluster, although year-to-year locations of clusters vary. Wildfires concentrated in Alaska and in Nenets, West Siberia and Chukotka sectors of the Russian Arctic. This is also true for the intensity of fires: in the five-year period the FRP values in some areas exhibited considerable spatial autocorrelation. Overall, Alaska was identified as the wildfire "hot spot" (a cluster of high intensity multiple fire events).

To analyze possible factors that determine spatiotemporal variation of arctic wildfires occurrence and intensity, we analyzed fire events in respect to geographic location (latitude/longitude), bioclimatic zones, vegetation types and proximity to points of human-caused disturbance (settlements, roads, pipelines, oil wells, etc.). The results clearly indicate the relationship between vegetation types and occurrences and intensity of wildfires: areas with larger amounts of combustible biomass and longer warm periods (mostly southern arctic ecosystems) having a greater number and more intensive fires. We were unable to detect a clear relationship between wildfire locations and elements of anthropogenic disturbance.