Effects on spectral reflectance from snow ageing (scientific note)

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This scientific note elaborates on the role that snow plays as an insulator for solar radiation on Arctic tundra and sea ice. We present spectral radiation data on i) surface reflectance, ii) attenuation in snow packs on land and on sea ice, and iii) under-ice irradiance. Our data is collected at Arctic tundra and fast-ice sites on Svalbard and in the Pechora Sea during spring melt-conditions. Although the spectrally-integrated surface reflectance, or albedo, decreases relative steadily in spring, we find that the infrared (IR) albedo decreases most strongly in the initial phase of snow melt while the visible albedo drops more quickly later on. The fact that the spectral signature of snow changes with time put restrictions on obtaining accurate satellite-derived narrow-band albedo measurements; however, new sensors will introduce significant improvements. Although thin, the presence of a snow cover fully dominates the exchange of solar radiation between the atmosphere and the sea ice-ocean system. Thus, a changing precipitation pattern (in time and space) in the Arctic Ocean can play a crucial role on sea-ice thickness distribution in a climate warming scenario. At last, this work suggests that the parameterisation of albedo in climate models could attempt to describe optical characteristics more realistically.
国立極地研究所の論文