An extended‐range Single Particle Soot Photometer (SP2) coupled to a Marin‐5 nebulizer was used to measure the refractory black carbon (rBC) mass and number size distributions in 1,004 samples from a West Antarctica snow/firn core. The SP2 was calibrated using Aquadag and a Centrifugal Particle Mass Analyzer for BC particles ranging from 0.5 to 800?fg. Our results indicate a significant contribution of rare, large particles of mass‐equivalent diameter (DBC)??500?nm to the total rBC mass (36%), while small particles (DBC??100?nm) are abundant but contribute 8% to total rBC mass. We observed a primary mass median diameter of 162?±?40?nm, smaller than reported for snow in other regions of the globe but similar to East Antarctica rBC size distributions. In addition, we observed other modes at 673, 1,040, and 1,810?nm (uncontained mode). We compared two sets of samples from different seasons (wet vs. dry) and observed that dry season concentrations are 3.4 and 2 times that of the wet season in the ranges of 80?nm??DBC??500?nm (small particles) and 500?nm??DBC??2,000?nm (large particles), respectively, while number of particles in the dry season is 3.5 and 2 times that of the wet season for the same size ranges. Millimeter thick melt layers have been observed in some samples, although they did not change the observed median diameter. This study provides the first detailed rBC mass and number size distribution from West Antarctica. Plain Language Summary Black carbon (BC) is a particle produced by the incomplete combustion of biomass burning and fossil fuels and plays an important role in the climate system due to its strong light absorption properties. The size of BC particles in snow is important for determining the effects that BC has on the cryosphere and provides insight into the processes controlling BC emission history, transport, and deposition. Past studies indicate spatial differences of BC size distributions in snow, but these studies are limited in number, and more are needed to address this spatial variability. Here the size distribution is presented of BC particles from 1,004 samples from a Pine Island Glacier ice core, West Antarctica, in a region where there is no information of BC particle size in snow. BC in West Antarctica is smaller than other regions of the globe but large, rare particles are also present. These large BC particles are larger than what other studies have reported and could be a result of long‐range transport from other continents and/or agglomeration from small particles during transport or deposition.
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