Long-term changes in the sea ice regime in the Baltic Sea near the Estonian coast

Long-term changes in the parameters of the sea ice regime (the date of appearance of the first sea ice in the beginning of winter, the date of the formation of fast ice, the date of the formation of young ice, the date of the break-up of fast ice, the date of the final disappearance of sea ice and the total number of days with sea ice) in the Baltic Sea near the Estonian coast are analysed for the period 1950/1951–2004/2005. Data were obtained from 8 stations at different coastal regions. Medians, quartile ranges and extremes were calculated. Spatial differences in the sea ice regime between different coastal regions of Estonia were determined. A statistically significant decrease in sea ice was detected that lies in a good correlation with the general warming trend in winter and spring during the same period. Large differences in the magnitude of the trends can be found between different coastal regions of Estonia. On the southern coast of the Gulf of Finland, long-term changes in sea ice parameters are small and mostly insignificant. The highest decrease in sea ice has been observed on the islands of the West-Estonian Archipelago, where the period with ice has decreased by 1.5–2.5 months. Possible causes for the spatial differences are discussed.