Unprecedented fire activity above the Arctic Circle linked to rising temperatures

Abstract

Arctic fires can release large amounts of carbon from permafrost peatlands. Satellite observations reveal that fires burned ~4.7 million hectares in 2019 and 2020, accounting for 44% of the total burned area in the Siberian Arctic for the entire 1982–2020 period. The summer of 2020 was the warmest in four decades, with fires burning an unprecedentedly large area of carbon-rich soils. We show that factors of fire associated with temperature have increased in recent decades and identified a near-exponential relationship between these factors and annual burned area. Large fires in the Arctic are likely to recur with climatic warming before mid-century, because the temperature trend is reaching a threshold in which small increases in temperature are associated with exponential increases in the area burned.

Recent massive expansion of wildfire and its impact on active layer over pan-Arctic permafrost

“…Siberia has been reported to be undergoing expansion of wildfire since the 21st century, and occurrence of fires has migrated northward to the Siberian Arctic in the last decade [29]. The years 2019 and 2020 experienced anomalously high burned area in northeastern Siberia [63], which accounted for about 44% of the total burned area in Siberian Arctic from 1982 and 2020 [23]. The belowground combustion is more important in northern boreal forests compared with southern stands [20].…”

“…Given that remote sensing datasets tend to underestimate wildfire activity especially in high latitudes [41][42][43], we evaluated the datasets used in this study with other studies on wildfires in high latitude regions. The burned area in 2020 Siberian Arctic (latitudes > 66.5 • N) was estimated between 1.71 and 2.62 Mha [23]. Burned area from FireCCI51 in this study was 2.39 Mha over Siberian Arctic in 2020 (figure S4(a)), within the burned area range retrieved from Sentinel-3 (C3SBA10) which is identified as one of the most accurate products in representing burned areas of Siberian wildfire in 2019 and 2020 [23].…”

“…The burned area in 2020 Siberian Arctic (latitudes > 66.5 • N) was estimated between 1.71 and 2.62 Mha [23]. Burned area from FireCCI51 in this study was 2.39 Mha over Siberian Arctic in 2020 (figure S4(a)), within the burned area range retrieved from Sentinel-3 (C3SBA10) which is identified as one of the most accurate products in representing burned areas of Siberian wildfire in 2019 and 2020 [23]. The mean burned areas of FireCCI51 during the growing season (May-September) of 2001-2014 in continuous and discontinuous permafrost were 2.70 and 1.58 Mha, respectively (figure S4(b)), which about doubles the burned area derived from an early version MODIS burned area product (MCD45A1) [44].…”

“…In addition to direct carbon emissions from organic matter combustion, wildfires over the permafrost may alter soil carbon fluxes for decades because wildfires modify soil physical and chemical properties, and decomposition processes [21]. As wildfires become more frequent and severe in boreal regions [22,23], the released carbon induced by wildfires from frozen soil may alter the global carbon budget and accelerate global and Arctic warming, thereby forming a positive feedback between permafrost degradation and climate warming [24,25]. Under a warming climate, wildfires can have a compounding effect with an accelerated temperature rise and permafrost thaw [26,27].…”

CALC-2020: a new baseline land cover map at 10 m resolution for the circumpolar Arctic

“…Accounting for ∼ 5.5 % of the Earth's land surface, the Arctic disproportionately affects global biogeochemical cycles (Jeong et al, 2018;Landrum and Holland, 2020;Miner et al, 2022) and harbours a large proportion of high-latitude biodiversity (Niittynen et al, 2018;Christensen et al, 2020). During the past decades, the Arctic as a whole has been rapidly warming (Previdi et al, 2021), with crucial consequences for the terrestrial environment including land ice retreat (Shepherd et al, 2020), permafrost thawing (Hjort et al, 2018), vegetation greening/browning Berner et al, 2020;Bartsch et al, 2020b) and intensified greenhouse gas emissions (Najafi et al, 2015;Descals et al, 2022). These changes have profound impacts on Arctic biomes (Hodkinson et al, 1998;Shevtsova et al, 2020;Wang and Friedl, 2019) and put millions of local residents and their cultures at risk (Huntington et al, 2019).…”