Unprecedented East Siberian wildfires intensify Arctic snow darkening through enhanced poleward transport of black carbon

Abstract

Summer Arctic black carbon (BC) predominantly originates from boreal wildfires, significantly contributing to Arctic warming. This study examined the impact of MODIS-detected extensive East Siberian wildfires from 2019 to 2021 on Arctic BC and the associated radiative effects using GEOS-Chem and SNICAR simulations. During these years, Arctic surface BC aerosol concentrations rose to 46 ng m^-3, 43 ng m^-3, and 59 ng m^-3, nearly doubling levels from the low-fire year of 2022. East Siberian wildfires accounted for 62 %, 75 %, and 79 % of elevated BC levels in 2019, 2020, and 2021, respectively. These wildfires also increased BC deposition on snow and sea ice, particularly in the Laptev and East Siberian Seas. The resulting snow contamination (30.6 ± 5.15 ng g^-1, 15.4 ± 1.29 ng g^-1, and 33.8 ± 5.24 ng g^-1) reduced surface snow albedo, increasing summer Arctic radiative forcing over snow and sea ice by +1.38 ± 0.65 W m^-2, +0.70 ± 0.20 W m^-2, and + 1.46 ± 0.73 W m^-2 in 2019, 2020, and 2021, respectively. As climate warming intensifies, more frequent extreme wildfires in East Siberia could further amplify Arctic snow darkening, potentially accelerating Arctic warming.

Keywords: Arctic; Black carbon; Deposition; Radiative forcing; Siberian wildfires; Snow albedo.