Solar radiation and ice melting in Lake Vendyurskoe, Russian Karelia

Field experiments were conducted during two melting periods, April 2006 and April 2007, in Lake Vendyurskoe. The observation programme included weather, ice and snow thickness and structure, water temperature and solar radiation transfer through the ice. Albedo showed a systematic decrease from 0.5–0.8 for wintertime dry ice and snow to 0.1 for wet bare ice in spring, with spatial standard deviation of about 10%. The e-folding depth of light level was 60–80 cm for congelation ice and 15 cm for snow-ice. Light transmissivity of the ice cover increased from melting but decreased from ice deterioration; it varied between 0.25–0.35 in 2006, while in 2007 there was a systematic trend from 0.1 to 0.5 in six days. The heat budget was governed by net solar radiation with daily peaks up to 400–500 W m⁻² on clear days. The average daily melt was 1.2 cm at the surface, 0.5 cm at the bottom and 1–2 cm (thickness equivalent) in the interior.