Friday, 7 June 2002: 9:45 AM
Spectral and total albedo of Antarctic sea ice
During two springtime voyages of the Australian National Antarctic Research Expeditions (ANARE) in the East Antarctic sea-ice zone, October-November 1988 and 1996, spectral albedo was measured in the ultraviolet, visible, and near-infrared, from 320 to 1060 nm wavelength. The surface types sampled were water, grease ice, pancakes, nilas, snow-covered nilas, grey ice, snow-covered first-year ice, bare fast ice, snow-covered fast ice, and tabular icebergs. For thin ice types the measurements were made from a basket hanging from the ship's crane, or from a helicopter.
The albedo of snow-free ice increases with ice thickness, from 0.07 for open water to 0.5 for 140-cm-thick bare ice; the corresponding visible albedos are 0.07 to 0.7. A thin coating of snow over sea ice causes the albedo to increase dramatically. Just 7 mm of snow raised the albedo of thick sea ice from 0.49 to 0.81, nearly as high as that of thick snow (0.83), in agreement with calculations of a radiative transfer model.
The spectral albedos are integrated to obtain band albedos for satellite channels and for GCM bands.