Relationships between the Baltic Sea ice extent and ice parameters in the sheltered basins of the southern Baltic coast

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 Łebsko, 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 – Państwowy 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.