Investigations of newly formed sea ice in the Cape Bathurst polynya: 1. Structural, physical, and optical properties

The physical, structural, and optical properties of newly formed ice types were studied in the Cape Bathurst polynya (71°N, 127°W) during fall freezeup in October to early November 2003. Variable meteorological conditions with occasional snowfall resulted in the formation of numerous ice types and surface conditions. Ice samples were collected from horizontally homogeneous surfaces representative of the area. Crystallographic analysis on 33 ice cores revealed highly variable growth conditions and formation mechanisms in the area. The mean fraction of granular ice was 33%, while intermediate granular-columnar and columnar ice contributed 37% and 30%, respectively. Salinity profiles in the ice were C-shaped and as the ice grew thicker, bulk salinities decreased according to 4.582 + 13.358/h_i (cm). These conditions resulted in brine volumes ranging from 4% to 46%. Bare ice surfaces commonly formed a high salinity brine skim layer due to brine expulsion. Salinities up to 40‰ were observed in this layer. Under suitable conditions frost flowers formed on the ice, and their presence was related to characteristic ice microstructure with crystals that appeared disc-like in shape. Fine-grained snow-ice was formed when snow merged with surface brine to create a complex hypersaline surface at the snow/ice interface. The spectral reflectance for the thin ice types was most strongly related to surface conditions. The presence of frost flowers significantly increased the reflectance independent of snow precipitation. Any increase in ice thickness was found to have little effect on the reflectance once a 20-30 mm thick snow layer was present.