Introduction - Freezing of Lakes and the Evolution of their Ice Cover - page 8

Fig. 1.5 Learning frozen lakes in the field is an essential corner stone of knowledge. Students of
winter limnology field course taking samples under guidance of teachers in Lake P ää j ä rvi, Finland

Croley and Assel 1994; Lepp ranta 1983; Yang et al. 2012) for the evolution of ice

thickness and temperature. Numerical sea ice models had been developed earlier (Maykut
and Untersteiner 1971; Semtner 1976; Saloranta 2000) and they could be utilized for lake
ice as well. The snow layer, which plays an important, interactive role in the evolution of
the thickness of ice, forms the most dif

ä

cult part of lake ice thermodynamic models.
Mechanical models have been developed for ice forces in the scales of man-made
structures (Korzhavin 1962; Michel 1978) and for drift

ice for whole lake basins

(Ovsienko 1976;Wake andRumer 1983; Lepp ranta andWang 2008). Ice drifts in very large

lakes, such as Caspian Sea and Lake Superior, as in oceanic basins, and also in this

ä

field
sea ice models were the basis of lake ice models (Doronin 1970; Hibler 1979; Coon 1980;
Wang et al. 2003). The drift of ice is forced by winds and currents, and the mobility of ice
is determined by its yield strength.
The Earth ed into lakes, rivers and seas. In cold regions, ice

occurs in these basins as lake ice, river ice, sea ice, and blocks of land ice 4 origin forming
the category of

' s surface waters are classi

fl floating ice. Rivers have a dynamic ice cover due to their permanent and

turbulent flow, resulting in abundance of frazil ice, anchor ice and ice jams. Sea ice forms

of saline water and contains brine, and sea ice basins have large length scale with drifting
ice. Small blocks of land ice can be found in proglacial lakes, but massive icebergs belong

fl

4 Land ice is glacial, brought to water bodies by calving of glaciers.