Mass concentration and origin of black carbon in spring snow on glaciers in the Alaska Range

Abstract

Black carbon (BC) is one of the light-absorbing particles that reduce the albedo of snow surfaces. Snow samples were taken from the surface of three glaciers in the Alaska Range in mid-April 2017. The BC size distribution and concentration were analyzed with a laser-induced incandescence (LII) method. The BC concentration of the snow samples was 1–6 μg L−1 and 0.5–3.1 μg L−1 at a depth of 0–2 cm (surface) and 2–10 cm (subsurface), respectively. These values are comparable to other Arctic areas and are considered to be the Alaskan background level. The BC concentrations are 0.5% of those of insoluble solid particles (ISPs) measured using an electrical sensing zone method. The surface albedo change due to BC and other ISPs concentrations was estimated to be 0.004–0.007 for the snow surface in April. The ablation at the observation sites on Gulkana Glacier would be 1.2% larger in the ablation season due to black carbon deposition. The chemical transport model revealed that 17%–34% of BC originates from biomass burning in Asia and Siberia, and 60% of BC originates from China in this study.