The relationship between air temperature (mainly winter, December-March) in Świnoujście, Gdynia, and Elbląg and ice parameters (dates of the first ice and disappearance of the last ice, the length of the ice season, number of days with ice, maximum ice height) of southern Baltic coastal lagoons (Szczecin, Puck, and Vistula) was investigated. Trends in these parameters were determined, too. The observation material comes from the archives of the Institute of Meteorology and Water Management and spanned the winters from 1950/51 through to 2019/20. Relationships between the selected ice parameters for the study basins and the values of air temperature were examined using correlation and regression methods. The regression equations and trends, as well as their correlation and determination coefficients, were determined. The statistical significance of these relationships was examined using the Fisher-Snedecor test. Strong correlations between ice parameters values and air temperature were obtained, characterized by high values of both correlation coefficients and statistical significance. All trends of ice parameters indicate mitigation of ice conditions. An acceleration in both temperature and ice condition mildening occurred in the late 1980s, and especially in the last years of the study period. These trends, except the first ice date, are statistically significant, some even at α < 0.001. The length of the ice season becomes significantly shorter, the number of days with ice and the maximum thickness is smaller, and the last ice is disappearing early. An increase in the correlation and determination coefficients and a characterized trend of ice parameters values towards the East was found. It shows the increased impact of a warming climate in this direction on the southern Baltic coast. Strong correlations and trends may be of prognostic significance.

Shallow, lagoonal coastal lakes of the Southern Baltic are exceptionally susceptible to atmospheric factors. This work examines the influence of winter air temperatures in Ustka on ice parameters (dates of first ice occurrence and last ice disappearance, ice season duration, number of days with ice, and maximum ice thickness) on Southern Baltic coastal lakes (Jamno, Bukowo, Gardno, Łebsko), and trends displayed by changes in these parameters over the period spanning 1960/61-2019/20. The research data was retrieved from the archives of Institute of Meteorology and Water Management – National Research Institute. As a first step of the analysis, we investigated the statistical relationships in spatial and temporal variations in winter air temperature and coastal lake ice parameters. Correlation and regression method was employed to determine the influence of air temperature on coastal lake ice conditions. Correlation and determination coefficients were calculated, and linear regression equations were determined. The statistical significance of the observed relationships was assessed using Fisher-Snedecor test. Additionally, linear trend models were constructed. Our analysis indicates that from 1960/61 to 2019/20, the average rate of increase in winter temperature (December-March) in Ustka equalled 0.04°C ⋅year^-1. The correlation coefficients for air temperature versus ice parameters were highly statistically significant (p<0.001). The strongest relationships (with correlation coefficients below -0.90) occurred between air temperature and number of days with ice. Ice season duration and number of days with ice are both closely linked with last ice disappearance date and ice thickness. Our analysis shows that a 1°C increase in average seasonal air temperature will result in the number of days with ice on the studied coastal lakes becoming reduced by 16-17 days. All trends in ice parameters indicate a mildening of ice conditions. Most of the assessed trends are statistically significant. The strongest trends were observed for ice season duration, and indicate its shortening toward the east, from 0.66 day ⋅year^-1 (Lake Jamno) to 1.16 day ⋅year^-1 (Lake Łebsko). All correlation coefficients for ice trends were found to increase eastward, which could be explained by an increasing influence of the warming climate over the Southern Baltic in this direction. The strong relationships between air temperature and Southern Baltic coastal lake ice parameters, and the determined rate of changes may have a significance for forecasting, as the shifting dates of ice formation and disappearance on lakes are highly important for the lake hydrodynamics, and the functioning of aquatic ecosystems.

We studied the phenomena associated with the thrusting of ice onto the shore of the Szczecin Lagoon based on the occurrence of tree ice scars. The measurements concerned mostly the maximum height, length and width of ice scars on trees, and the distance of these trees from the shore in the period 2017–2022. It was observed that sheets of ice advanced up to 64 m inland, and piled to form hummocks reaching up to 4.3 m above the water level. These maximum values occurred mostly on eastern shores, which is where the highest numbers of damaged and broken trees were observed. This should be associated with the strongest and most frequently occurring wind blowing from the western direction in the winter-spring period. To the contrary, the lowest number of damaged trees were observed on the western shore. This is due not only to the lower frequency of wind blowing from the east, and the associated cooling (Ta < 0°C) and ice cover stabilization, but also due to the presence of extensive reed belts. Our results enable an indirect insight into the ice phenomena dynamics, especially in areas lacking systematic ice observations. Similar conclusions may be extended for all the sheltered basins as lakes or lagoons.

In this study, climate change was described by area-averaged annual precipitation totals and area-averaged mean annual temperature values in each catchment area, while water resources were described by mean monthly specific discharges in these catchments. Thirty-seven catchments located entirely in lowland areas of Poland were selected for the analysis. The research was conducted based on data from hydrological years 1961-2021. In order to compare changes in annual precipitation totals and mean annual air temperature values with changes in annual mean specific discharge, linear trends of the mentioned variables were determined. The effect of precipitation totals and air temperature on specific discharge in individual catchments was determined using multiple regression. Statistically significant increase in the value of mean annual air temperature was recorded for all studied catchment areas. In none of the examined catchments were the changes in annual precipitation totals statistically significant. Analysis of the time trends of specific discharge showed statistically significant decreases in their annual mean values in almost half of examined catchments. The correlations between specific discharge, air temperature and precipitation totals are not very strong, which is mainly due to the strong impact of other, anthropogenic factors on water management.The greatest negative changes are observed in the central part of Poland. Specific discharge is more strongly dependent on precipitation totals than on temperature, with the effect of air temperature only being reflected in the volume of water resources after a certain period of time.

In the study, archive data on the maximum annual ice extent in the Baltic Sea (MIB) for the period 1961-2018 were used. They were obtained from the FIMR database. Data on ice parameters for the four largest southern Baltic coastal lakes: Jamno, Bukowo, Gardno and Lebsko, and for Szczecin, Puck, and Vistula Lagoons, come from the Maritime Branch of Institute of Meteorology and Water Management - National Research Institute (in Polish: Instytut Meteorologii i Gospodarki Wodnej - Panstwowy Instytut Badawczy, IMGW-PIB) in Gdynia. The time series for the lakes cover the years from 1960 to 2018, and for the lagoons - from 1946 to 2018. Three ice parameters were selected for this study: the number of days with ice, the duration of the ice season and the maximum ice thickness for a given winter. Relationships between the selected ice parameters for the studied basins and the MIB were examined using correlation and regression methods. Correlations between the MIB and values of the ice parameters for the lakes and the southern Baltic coastal lagoons do not differ significantly. Considerable differences are observed amongst the correlation coefficients for individual ice parameters and the MIB. Larger differences are found in relationships between the values of individual ice parameters in the sheltered basins and the MIB. The strongest correlation with the MIB is observed for the maximum ice thickness and the number of days with ice.