Effect of climatic changes on the development of the thermal-ice regime based on the example of Lake Charzykowskie (Poland)

Abstract. The paper discusses the course of air temperature in the years 1961-2014 in Chojnice (Central European Lowland), and its effect on water temperature and occurrence of ice cover on Lake Charzykowskie. An increase in mean annual air temperature was determined by 0.31oC per 10 years, and its even faster increase in the winter season (December-March), by 0.37oC per 10 years on average. An increase in mean annual water temperature in the lake by 0.24oC per 10 years also occurred. An increase in air and water temperature in winter months caused a reduction of the period of occurrence of ice cover. In the years 1961-2014, the persistence of ice cover was subject to a decrease by 3.7 days per 10 years on average, and the mean thickness of the ice cover decreased from 30 to 19 cm