CODEX Entry 3103: Baltic Sea Ice
Due to the low salinity in the Baltic Sea, the area of the winter ice varies from 10% to 100% each year. The ice coverage peaks in late February. Since 1720, it has frozen over entirely 20 times, most recently in 1987, which was the most severe winter in Scandinavia since 1720. The ice then covered 400,000 km2. During the winter of 2010–11, which was severe compared to those in the preceding two decades, the maximum ice cover was 315,000 km2, which was reached on 25 February 2011. The ice then extended from the north down to the northern tip of Gotland, with small ice-free areas on either side, and the east coast of the Baltic Sea was covered by an ice sheet about 25 to 100 km wide all the way to Gdańsk.