Future of Frozen Lakes - Freezing of Lakes and the Evolution of their Ice Cover - page 269

9.1 Role of Ice Cover

Lake ice forms in cold regions, where the air temperature goes below the freezing point in
winter. Ice is normally seasonal but in high latitudes and high altitudes permanently ice-
covered lakes are found. The presence of seasonal lake ice may last more than half a year,
and its thickness can reach up to 2 m. The snow and ice season modi es the hydrological

year in cold regions by its in uence on the annual distribution of runoff and by the

problems caused by ice to the management of water resources. The research of freezing
lakes has experienced a major rise after the year 2000, much due to environmental and
climate problems in addition to basic science (Fig. 9.1 ).
Lake ice is a degree more simple as compared with sea ice and river ice (Fig. 9.2 ). Lake
ice cover is mostly immobile and circulation in the water body beneath the ice cover is
weak, and in particular, freshwater lake ice is poor in impurities. But lakes with strong
through

fl

flow may have river ice type processes (Ferrick and Prowse 2002; Shen 2006), ice
structure in brackish and saline lakes is similar to sea ice, and drift ice occurs in very large
lakes. Our knowledge of ice in saline waters comes mainly from marine research (e.g.,
Wadhams 2000; Weeks 2010), and these results are to a large degree applicable for saline
lakes. Hypersaline lakes would require speci

fl

c lake water analyses for ice research rather

than extrapolation of the sea ice knowledge.

Fig. 9.1 Students taking water samples from beneath lake ice