Variation in the Ice Cover Thickness on Lake Samołęskie as a Result of Underground Water Supply

The character of phenomena related to freezing depends on macroscale factors and mainly on thermal conditions, but local conditions can also be of great importance in shaping the course of these phenomena. Building of ice cover can be substantially different even for neighbouring lakes as a result of different individual features such as, for example, morphometric parameters. In this study the variation in the thickness of ice cover on Lake Samołęskie (29 ha) localised in western Poland, is analysed. According to measurements performed the differences in the thickness of ice cover was significant as it varied from 20 to 33 cm. A characteristic feature was that along the west bank of the lake the ice cover was thinner and its thickness increased towards the east. Analysis of the hydrogeological data revealed that this phenomenon is related to the supply of water to the lake basin by efficient water-carrying formations. The influx of water affects the bottom layer of the ice cover. This effect is aggravated by the fact that the water is supplied under elevated pressure as evidenced by the presence of a polynia of about 10 m in diameter, over the deepest (over 20 m deep) site in the lake. The polynia is never frozen, even during the coldest winters. The specific features of the lake illustrate the influence of local geological conditions on the character of processes taking place in lakes in general.