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The Distribution of Soot Contamination in the Vicinity of the SHEBA Ice Station and Implications for Radiative Energy Balance |
University of Washington, University of Washington, USA CRREL Alaska
tcg@atmos.washington.edu
Soot observations around the periphery of the Arctic Ocean (Clarke and Noone, 1985) indicate snow pack concentrations ranging from about 1 to more than 200 nanograms of carbon per gram of snow (ng/g), with typical values being near 40-50 ng/g. Values of this magnitude would affect not only the albedo and transmissivity of the ice cover, but also surface melt rates and internal heat storage in the ice. During SHEBA, there was concern that soot emitted from the ship might adversely impact the surface albedo and the heat and mass balance, producing results that would not be representative of the region as a whole. To investigate this possibility, a series of measurements of soot content in the snowpack were carried out starting in the spring of 1998, during the time of maximum snow accumulation. Average soot levels in the snow ranged from 1-7 ng/g on the upwind side of the ship, where the heat and mass balance program was carried out, to as high as 35 ng/g on the downwind side. Results from the upwind side of the ship were essentially the same as background values measured at distances of up to 16 km from the ship. These results suggest that concentrations in the Central Arctic Basin are substantially lower than those found in the coastal regions and would decrease the spectral albedo at visible wavelengths by less than 0.01. A detailed description of the spatial distribution of soot concentration will be presented and compared with results. A detailed description of the spatial distribution of soot concentration will be presented and compared with results from radiative transfer calculations modeling the effects of this soot on the optical properties of the ice and snow and on the heat and mass balance of the ice cover.
