Author(s): P. E. Bond
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Keywords: No Keywords
Abstract: Beam-spread measurements were performed on first-year sea ice, and laboratory grown NaCl ice, to determine the influence of the ice structure on light propagation at optical wavelengths. An extensive set of beam-spread profiles for both sea ice and snow-covered sea ice encompassing ice stations in McMurdo Sound, Antarctica, the Ross Sea during both winter and summer, as well as laboratory grown NaCl ice, were fitted using empirical Monte Carlo models. The transport scattering rates determined from the Monte Carlo models showed relationships with both the temperature and salinity of the upper surface of the sea ice, while those collected from the snow-covered sea ice were shown to depend on snow grain size. Fitting of beam-spread profiles, using a Monte Carlo model whose transport scattering rates were based on the physical properties of the ice, was successful for sea ice from McMurdo Sound. The model used air, brine and salt fraction profiles measured throughout the depth of the ice, and determined scattering rates for the ice using these profiles, as well as the assumed dimensions of the air bubbles and salt crystals. Brine inclusion dimensions were left as fittable parameters. A measured beam-spread profile was fitted by assuming physically realistic inclusion sizes, including elongated, vertically orientated brine inclusions, resulting in anisotropic scattering rates which allow light to propagate more easily in the vertical direction within the ice. A possible but not significant preferential direction for the horizontal propagation of light was found in firstyear ice. This direction was found to approximately coincide with the basal planes of the aligned ice platelets observed at depths greater than 0.2 m.
Year: 2002