Keywords:Black carbon, Wet deposition, Arctic
Black carbon (BC) deposited on snow lowers snow albedo, potentially contributing to the warming in the Arctic. The distributions of inorganic aerosols (ions), which contribute to direct and indirect aerosol effects, are also greatly influenced by deposition. It is critically important to measure the spatial distributions of BC and ions in snowpack in different regions of the Arctic to quantify these effects. Because accurate measurements of BC and ions in snowpack are very limited, we measured the mass concentrations of size-resolved BC (CMBC) and ions in snowpack over Finland, Alaska, Siberia, Greenland, and Spitzbergen in early spring during the period of 2012 – 2016 by using a single-particle soot photometer and ion chromatography, respectively. BC deposition amounts (DEPMBC) during snow accumulation periods were derived from CMBC and snow water equivalent (SWE). Detailed analyses have shown that the spatial distributions of the anthropogenic BC flux and topography strongly influenced the latitudinal variations of CMBC and BC size distributions. The average size distributions of BC in snowpack shifted to smaller sizes with the decrease in CMBC, likely due to an increase in the removal efficiency of BC with the increase in BC diameter during transport from major BC sources. The present CMBC were much lower than previous CMBC measured by using an Integrating Sphere/Integrating Sandwich spectrophotometer by a factor of about 13. The present accurate data of CMBC, SWE, and DEPMBC are very useful in constraining climate model to estimate the effect of BC on the climate of the Arctic.