Author(s): Ants Erm; Juho Jakkila; Ruibo Lei; Elina Jaatinen; Matti Lepparanta
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Keywords: Lake ice; Snow; Optics; Reflectance; Attenuation coefficient
Abstract: Field programme on light conditions in ice-covered lakes and optical properties of lake ice was performed in seven lakes in Finland and Estonia. Based on irradiance measurements above and below ice, spectral reflectance and transmittance were determined for the ice sheet. Beam attenuation spectra c (λ) and suspended matter concentrations C of melted ice samples were determined in the laboratory. Snow cover was the dominant factor for transmission of irradiation into the lake water body, due to its large reflectance (up to 95% at 500 nm) and attenuation coefficient. Diffuse attenuation coefficients varied from 10 to 20 m for snow and from 0.6 to 3.4 m for ice. Attenuation coefficients of snow were meanly 5 times higher as these of ice. A dependence of attenuation on optically active substances in ice was followed. The concentration of suspended matter reached 30 to 50 g m in some ice layers but mainly it stayed in the range2.5–5 mg m.
Year: 2010