Soot in the arctic snowpack: a cause for perturbations in radiative transfer

Recent data collected in the Arctic have demonstrated the transport of atmospheric aerosol of anthropogenic origin into that region. Concern over the radiative effect of the highly-absorbing soot component of this aerosol has resulted in a variety of atmospheric sampling efforts aimed at assessing the climatic impact of this component. However, little attention has been given to the measurement of soot deposited on the Arctic snowpack and the resulting perturbation of snow albedo, snowmelt rates and radiative transfer. Here we report measurements of light-absorbing material in the Arctic snowpack for longitudes from 25 E to 160 W. The contributions to light absorption due to natural crustal and soot aerosol are identified by their wavelength dependence. Reductions in Arctic snow albedo of one to several percent appear probable for the soot/ice mass fractions obtained to date. Estimates of the impact of this reduced albedo on the Arctic radiation budget over a season are shown to approximately equal that of the Arctic haze itself. The absorption of shortwave radiation by the springtime snowpack is estimated to be 5–10% higher than that of soot-free snow for this data.