Thermal conditions in Lake Skärsjön
Bathymetric chart of Lake Skärsjön.
Several lakes in Sweden are named Skärsjön. This lake Skärsjön is a small, wind-sheltered lake, situated about 20 km ENE of the city of Uppsala. For morphometric data, see Axelsson 1957 (Geographica 31).
Water temperatures in the Swedish lake Skärsjön 18/1 - 9/5 1948. From Axelsson 1957, Geographica 31 (Naturgeografiska uppsatser. Redigerade av Filip Hjulström och Valter Axelsson).
In the winter of 1948 the temperature of the bottom water was higher than the thermical density maximum, +4oC. The greater density of the bottom water was due to its higher content of dissolved and colloidal matter. The onset of freezing occurred at a relatively early date, and the maximum thickness of the ice was 50 cm. A great amount of melt-water could therefore be obtained from the ice during the later part of the winter, and the chemical stratification of the upper water layers could become stable. The winter stratification passed directly into summer stratification without any preceding period of circulation. The ice break-up took place on 14. April, but the water did not begin to circulate until 2. May.
Accumulation and loss of heat in Lake Skärsjön 4/11 1948 - 4/12 1949. From Axelsson 1957, Geographica 31. (Also in Fizikogeograficheskiy Atlas Mira, 1965.)
If the onset of freezing begins early, the mean temperature of a temperate lake is usually relatively high, and a great deal of heat is conducted from the bottom. This is an especially significant factor for the temperature conditions in shallow, temperate lakes during the winter. If, on the other hand, the onset of freezing occurs later, the water body and the bottom deposits have probably lost a great deal of heat, and the mean temperature of the lake is therefore low during the winter.
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