Lake Water Body in the Ice Season - Freezing of Lakes and the Evolution of their Ice Cover - page 232

Fig. 7.14 Time series from the melting season in Lake Vendyurskoe, Russian Karelia, April 2006
(Lepp ä ranta et al. 2010). a Albedo; b quantum downwelling PAR irradiance in the surface, snow-ice
and congelation ice (the depths were 0, 14 and 39 cm at the beginning, and 0, 3, and 28 cm at the
end due to surface melting)

For a normal three-layer ice sheet, the light transmittance is given by Eq. ( 3.24 ). For
bare congelation ice the transmission is lowered due to the increased surface re

fl ectance

but a snow cover makes a big difference due to its very high re ectance and rapid light

attenuation: e.g., adding 10 cm snow on a 50 cm ice sheet can reduce the irradiance level
beneath the ice by an order of magnitude. In spring, sunlight plays a major role in the
melting of the ice.

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