Spatial Variation of, and Correlations Among, Snow Surface Albedo and Physical Parameters of Summer Snow Cover on Sea Ice in the Ross Sea, Antarctica

All-wave albedo and spectral albedo of snow on sea ice were measured in the Ross Sea during a cruise in January-February, 1999. Concurrent measurements of physical parameters of the snow cover such as composite snow grain size, single snow grain size, snow mass density, snow surface temperature, and snow stratification were carried out. Snow particles in each 3 cm deep sample (volume 100 cm^-3) were described in terms of shape and general appearance using standardized terms, i.e., facets, striates, meltclusters, chains of grains, etc., and the relative proportion of each particle type with average radius <r> were determined. Most of the snow samples had undergone some metamorphosis. As a consequence, the particles were divided into two categories: the overall centimeter-order size of the larger, composite grains such as meltclusters, and the millimeter-order size of the grains (single grains) that made up the meltclusters. Based on these in situ measurements, three statistically average grain size models (equal grain number model, size distribution integrated average model and effective radius model) are used for the relation analyses between albedo and snow grain size for the two categories (composite grain and single grain). Correlations between albedo and snow physical parameters show that summer snow albedo is more sensitive to the snow cluster grain size than the single snow grain size for the top 9 cm of the snow cover. The strongest correlation is observed for the top 3 cm of snow. Coefficients and significance of correlation between albedo and composite grain size decrease with snow depth. Correlation analyses between albedo and composite grain number density show that in the top 9 cm of the snow cover, albedo is strongly correlated with the composite grain number density: the larger the number density of composite grains of the snow surface layer, the higher the albedo. This correlation decreases with depth. The same analyses for the single grain size and single grain number density show that there is no significant correlation between albedo and single grain size or between albedo and single grain number density. From the correlation analyses between albedo, snow surface temperature and composite grain size, it is found that the lower the surface temperature and the smaller the surface composite grain size, the higher the albedo. Spatial variation analyses of snow albedo and physical parameters show that in the Ross Sea pack ice there are notable latitudinal variations in albedo and physical snow parameters. As the ship moved southward through the pack ice: the snow surface temperature decreased; albedo was higher; the snow mass density was higher; the snow composite grain size decreased; and the number density of composite grains increased. All-wave albedo in visible and near infrared were lower at ice edges than at central pack ice due to larger grain size and lower number density.