Lake Water Body in the Ice Season
The annual cycle of cold region lakes is influenced by the ice formation. Seasonal ice cover is typical in the boreal zone, while a perennial lake ice cover occurs in some high polar or high mountain lakes. The ice cover buffers the surface water temperature to the freezing point and largely decouples the water body from the atmosphere. The circulation changes from wind-driven to thermohaline (Kirillin et al. 2012b). Processes beneath the ice are slowed down, and lake memory effects extend over the winter. In the ice season, the inflow and outflow also normally decrease. The heat storage of the bottom sediments becomes an important source (Falkenmark 1973), and heat leakage is only by molecular conduction through the ice cover. Oxygen is consumed especially in the bottom waters of eutrophic lakes, and the primary production becomes light-limited in snow-covered frozen lakes.