The Structure and Thickness of Lake Paeaejaervi Ice

Lake Paeaejaervi in southern Finland freezes over every winter and the ice cover is static. The structure of the ice in the lake has been mapped in 1993-1999. The ice thickness ranged from 31 to 70 cm, and the ice sheet consisted of two layers: columnar or macro grained congelation ice and fine grained snow-ice. The snow-ice portion was 10-43%. The average thicknesses were: 46 cm for total ice, 12 cm for snow-ice and 9 cm for snow. The maximum annual ice thickness showed rather weakly increasing level with decreasing mean winter air temperature. The grain size of snow-ice was typically 1-5 mm with maximum 8-9 mm. The congelation ice showed large macrocrystals, some columnar, with dimensions from 2 cm to more than 10 cm, columns were 2-4 cm in diameter and more than 10 cm in height. Prior to the snow-ice formation the snow layer was compacted in slushing to the fraction of about 2/3. The ice meltwater had the following properties: the conductivity (at 25 degree C) was 7-18 mu S/cm, pH was 6.1-7.3, and the contents of soluble and suspended matter were 8-18 mg/l and 1.0-2.5 mg/l, respectively. The conductivity and soluble matter contents were 10-20% of that of the lake water.