Multi-year black carbon observations and modeling close to the largest gas flaring and wildfire regions (Western Siberian Arctic)

Abstract. The influence of aerosols on the Arctic system remains associated with significant uncertainties, particularly concerning black carbon (BC). The polar aerosol station "Island Bely", located in the Kara Sea (Western Siberian Arctic) was established to enhance aerosol monitoring in the Arctic. Continuous in-situ measurements from 2019 to 2022 revealed the long-term effects of light-absorbing carbon. During the cold period, the annual average light absorption coefficient was 0.7 ± 0.7 Mm⁻¹, decreasing by approximately 2–3 times during the warm period. The interannual mean showed a peak in February (0.9 ± 0.8 Mm⁻¹), a ten times lower minimum in June, and exhibited high variability in August (0.7 ± 2.2 Mm⁻¹). The absorption Ångström exponent indicated presence of mixed and aged BC. An increase of up to 1.5 at shorter wavelengths from April to September suggests contribution from light absorbing brown carbon. The annual mean EBC demonstrated considerable interannual variability, with the lowest in 2020 (24 ± 29 ng m⁻³). Significant difference was observed between Arctic haze and Siberian wildfire periods, with record-high pollution levels in February 2022 (110 ± 70 ng m⁻³) and August 2021 (83 ± 249 ng m⁻³). During the cold season, 92 % of surface BC was attributed to anthropogenic sources, mainly from gas flaring. In contrast, during the warm period, Siberian wildfires contributed to BC concentrations by 47 %. Notably, unprecedented smoke was transported from Yakutian wildfires at high altitudes in August 2021, marking the most severe fire season in the region over the past four decades.