Abstract
Abstract. There are a large number of geophysical processes affecting sea level dynamics and coastal erosion in the Baltic Sea region. These processes operate on a large range of spatial and temporal scales and are observed in many other coastal regions worldwide. This, along with the outstanding number of long data records, makes the Baltic Sea a unique laboratory for advancing our knowledge on interactions between processes steering sea level and erosion in a climate change context. Processes contributing to sea level dynamics and coastal erosion in the Baltic Sea include the still ongoing viscoelastic response of the Earth to the last deglaciation, contributions from global and North Atlantic mean sea level changes, or contributions from wind waves affecting erosion and sediment transport along the subsiding southern Baltic Sea coast. Other examples are storm surges, seiches, or meteotsunamis which primarily contribute to sea level extremes. Such processes have undergone considerable variation and change in the past. For example, over approximately the past 50 years, the Baltic absolute (geocentric) mean sea level has risen at a rate slightly larger than the global average. In the northern parts of the Baltic Sea, due to vertical land movements, relative mean sea level has decreased. Sea level extremes are strongly linked to variability and changes in large-scale atmospheric circulation. The patterns and mechanisms contributing to erosion and accretion strongly depend on hydrodynamic conditions and their variability. For large parts of the sedimentary shores of the Baltic Sea, the wave climate and the angle at which the waves approach the nearshore region are the dominant factors, and coastline changes are highly sensitive to even small variations in these driving forces. Consequently, processes contributing to Baltic sea level dynamics and coastline change are expected to vary and to change in the future, leaving their imprint on future Baltic sea level and coastline change and variability. Because of the large number of contributing processes, their relevance for understanding global figures, and the outstanding data availability, global sea level research and research on coastline changes may greatly benefit from research undertaken in the Baltic Sea.
Highlights
Regional climate change in the Baltic Sea basin has been systematically assessed in two comprehensive assessment reports initiated by the Baltic Sea Experiment (BALTEX) and its successor Baltic Earth: BACC I (BACC Author Team, 2008) and BACC II (BACC II Author Team, 2015)
Many of the processes determining sea level dynamics and coastline change are relevant in the Baltic Sea where their relative contribution to the overall changes vary over short distances and across timescales
This has substantially contributed to the expansion of general concepts and of our present understanding of sea level and coastline change, and has fostered a regional understanding of the implications of climate change in the Baltic Sea
Summary
Regional climate change in the Baltic Sea basin has been systematically assessed in two comprehensive assessment reports initiated by the Baltic Sea Experiment (BALTEX) and its successor Baltic Earth (https://baltic.earth, last access: 13 August 2021): BACC I (BACC Author Team, 2008) and BACC II (BACC II Author Team, 2015). The area comprises some of the longest available tide-gauge records worldwide and much longer observational evidence This information has challenged our understanding of sea level dynamics and land movements associated with the glacial isostatic adjustment (GIA) (e.g., BIFROST project members, 1996) and has contributed significantly to our present understanding of large-scale sea level changes on a global scale. Timescales of processes and forcings vary considerably, ranging from a few seconds (e.g., wind waves) to millennia (e.g., GIA) This enables researchers to study a wide range of phenomena with larger and global relevance (e.g., glacial isostasy or characteristics of relative sea level changes).
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