Black carbon aerosols over coastal Antarctica and its scavenging by snow during the Southern hemispheric summer

Abstract

Mass concentrations of aerosol black carbon (BC) and of the composite (total) aerosols (M_B and M_T, respectively) were measured over two Antarctic locations, Maitri [70°S, 12°E, 123 m mean sea level (msl)] and Larsemann Hills (LH; 69°S, 77°E, 48 m msl) as a part of the twenty-eighth Indian Scientific Expedition to Antarctica during the Southern Hemispheric summer of 2009. Despite being very low compared to Northern Hemisphere locations, M_B and its mass mixing ratio to the total aerosols were much high over Maitri (~75 ng m^-3 and 2%) compared to LH (13 ng m^-3 and 0.2%). At both locations, M_B fell abruptly after blizzards, after which the values reduced to nearly half the pre-blizzard values. This BC scavenging by snow can lead to change in snow albedo and has strong climate implications. The Angstrom exponent (α_abs) estimated from the spectral values of absorption coefficients (σ _abs) is found to vary from 0.5 to 1, indicating higher a BC-to-organic carbon ratio typical of fossil fuel origin.