| Summary: | These data give estimates of black carbon (BC) mixing ratios from samples of snow or melting sea ice gathered by ourselves or by volunteers, mostly from 2006 to 2009 but with some data from earlier years. Almost all samples were collected in the spring season (March to early May) when the combination of snow cover and exposure to sunlight is maximized, and before the snow had started to melt. In many locations (Canadian Arctic, Russia, Greenland, Troms*oslash* and Ny *Aring*lesund) samples were gathered at intervals throughout the snowpack depth, giving information on the seasonal evolution of BC concentrations as the snow accumulated (and/or sublimated) throughout the winter. In addition to estimated BC mixing ratios, we give maximum possible BC concentration, the absorption Angstrom exponent of all light-absorbing aerosol in the snow, and the fraction of spectrally-integrated, solar-spectrum-weighted absorption by non-BC absorbers.
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