%0 Journal Article
%T Radiative characteristics of ice-covered fresh- and brackish-water bodies
%A Arst
%A Helgi
%A Erm
%A Ants
%A Leppˋranta
%A Matti
%A Reinart
%A Anu
%J Proceedings of the Estonian Academy of Sciences. Geology = Teaduste Akadeemia toimetised.
%D 2006
%I 
%X The structure and optics of ice and snow overlying bodies of water were studied in the years 2000每2003. The data were collected in the northern temperate region (nine Estonian and Finnish lakes and one brackish water site, Santala Bay, in the Gulf of Finland). In the present paper we describe the results concerning the radiative characteristics of the system ※snow + ice cover on the water§: albedo, attenuation of light, and planar and scalar irradiances through the ice. The basic data consist of irradiance measurements above and below ice cover for the PAR band of the solar spectrum (400每700 nm). Albedo varied across wide limits (0.20每0.70 for ice, 0.63每0.94 for snow), depending on the optical and physical properties of ice/snow and weather conditions. The vertically averaged light attenuation coefficient of the ice layer in the brackish waters of Santala Bay was higher than that in the lakes. The ratio of irradiance beneath the ice to incident irradiance increased 2.5每20 times after removing the snow, depending on the albedo and the thickness of ice and snow as well as on their optical properties. In the upper layer of water beneath the ice the ratio of planar to scalar quantum irradiances increased with depth (according to our earlier results obtained in summer this ratio decreased with increasing depth).
%K ice optics
%K albedo
%K under-ice irradiance
%K euphotic zone
%U http://kirj.ee/public/va_ge/geo-2006-1-1.pdf