Trends in ice conditions in the Gulf of Bothnia: case study with channel markers

Plans for new offshore wind farms in the northern part of the Baltic Sea are increasing drastically. Need for accurate and up to date information on ice conditions and ice interaction with the structures are even more important than earlier as offshore wind farms are being planned for more severe ice conditions. At the same time with increasing amount of offshore wind farm plans, ice conditions are predicted to get milder because of the climate change. To get an understanding on the already happened changes in the Gulf of Bothnia, ice conditions in channel markers and the selected points from the middle of the sea area were studied from the winter 1980/1981 to the winter 2021/2022. Digital and digitalized ice charts created for navigational purposes by the Finnish Ice Service were utilized. In this paper, the emphasis is on local-scale changes in parameters relevant for offshore wind turbine design. Ice conditions from the selected channel markers and the selected points from the middle of the sea area in the Gulf of Bothnia are given, and the recent changes are presented and discussed.