Long-Term Observations of Levoglucosan in Arctic Aerosols Reveal Its Biomass Burning Source and Implication on Radiative Forcing

Biomass burning (BB) has a significant influence on the Arctic environment. Here, we determined the atmospheric levels of BB-specific tracer compounds such as levoglucosan (Lev), galactosan (Gan), and mannosan (Man) in Arctic aerosols during 2010-2018. The average concentrations of Lev during the study period ranged between 0.43 and 4.15 ng m(-3). Both Lev/Man (0-30) and Man/Gan (0-3) ratios further suggested their origin from softwood/hardwood burning. The North Atlantic Oscillation (NAO) was the main driver of the Lev variability during the study period and Lev could be advected to Arctic air during the NAO was in a positive phase. Based upon the levels of Lev, black carbon (BC) generated from BB was estimated, and the corresponding radiative forcing was then calculated by Santa Barbara DISORT Atmospheric Radiative Transfer. BC has a potential warming effect in the atmosphere (+4.28 W/m(2)) while shows a cooling effect on the surface, which is equivalent to a large volcanic eruption (-3 W/m(2)). Since climate change is expected to intensify BB around the Arctic, such BC aerosols should be considered in future climate model projections.