Attribution of alterations in coastal processes in the southern and eastern Baltic Sea to climate change-driven modifications of coastal drivers

The main drivers of coastal processes, such as wave activity, variations in the water level, ice cover, and wind drift, may act differently in different segments of marginal seas with complex shapes. We analyse how the relative role of these drivers on the evolution of sedimentary shores changes along the southern and eastern Baltic Sea. While changes in the average water level have a strong impact along the southern shores of the Baltic Sea, rapid increases in the water level extremes affect most of the eastern subbasins of the Gulf of Finland and Gulf of Riga. The presence of a two-peak structure of predominant winds creates a fragile balance of alongshore sediment transport on the northeastern part of the Baltic proper and the Gulf of Riga. This balance could be changed by a rotation of predominant wave directions by a few degrees. Severe waves usually occur on the southern shores of the sea during water levels that are close to the long-term mean, while synchronisation of strong waves and high-water level is common on the eastern shore. The presence of sea ice is uncommon and insignificantly damps coastal processes in the southern part of the sea but the frequent presence of ice cover and freezing temperatures during the windy season stabilise the beaches of the north-eastern shores. Climate driven changes in ice cover duration may lead to erosion of many beaches in this part of the sea. The core message is that the impact of a single manifestation of climate change may vary greatly in different parts of the Baltic Sea and the reaction of coastal processes to this impact is substantially site-specific.