Ice Regime of the Kozłowa Góra Reservoir (Southern Poland) as an Indicator of Changes of the Thermal Conditions of Ambient Air

Abstract

Ice phenomena are construed as the occurrence of ice in water irrespective of its structure, form, and duration. One of the most frequently discussed research problems is the possibility of using long-term ice phenology as an indicator of changes of the thermal conditions of ambient air. The study used correlation analysis and regression models in order to determine changes in the parameters studied over time. In order to compare the ice regime of the study reservoir and other lakes in the region, discriminant function analysis, principal components analysis (PCA), and canonical redundancy analysis (RDA) were applied. During the 52 winter seasons studied (1964–2015), there were weak but still statistically significant trends concerning the increase in air temperature in the region (by 0.3 °C per decade), the reduction in the number of days with ice cover (by 8.6 days per decade) and the decline in the maximum and average thicknesses of lake ice (by 2.0 cm and 1.2 cm per decade). The low average depth and volume capacity are reflected in the rapid freezing rate of the reservoir, and its location results in a longer duration of ice cover, greater ice thickness, and later dates of its melting.