Relict glacial landforms in the southern Baltic Sea Basin

The seafloor geomorphology of glaciated continental margins occasionally hosts relict glacial landforms that serve as proxies of the ice sheet dynamics. The Baltic Sea is a relatively shallow, epicontinental, young sea whose formation after the last deglaciation was modulated by global sea-level fluctuations and isostatic adjustments. During the last glaciation, the Baltic Basin (BB) was one of the major advance corridors of the Fennoscandian Ice Sheet (FIS) towards the Central European Plain. It hosted the Baltic Ice Stream Complex – a zone of potentially highly dynamic, warm-based, fast-flowing ice that drained central parts of the ice sheet. Therefore, BB is a key region for reconstructing the dynamics of the last FIS southern sector. However, the availability of high-resolution bathymetric data which may better constrain BB’s geomorphology is still limited. In particular, the southern part of the BB suffers from a lack of high-resolution bathymetry, which leaves glacial landforms, potentially preserved at the seafloor, largely unrecognized. Here, we present the results of mapping relict glacial landforms in some areas of the southern BB. The landforms were mapped in ArcGIS based on bathymetric models obtained from the Polish Navy Hydrographic Office, the Swedish Maritime Administration, the General Inspectorate of Environmental Protection, and the Rhenish-Westphalian Power Plant as 0.5 to 10 m grids. We identified individual glacial landforms such as subglacial lineations, subglacial ribs, moraine ridges, grounding line landforms, crevasse-squeeze ridges, meltwater channels, eskers and ploughmarks. The mapping was performed by on-screen digitizing at various scales, depending on landform dimensions. The outcome is a GIS map of glacial geomorphological features preserved at the seafloor. This is the first map displaying the distribution and morphology of relict glacial landforms based on high-resolution bathymetric data in the southern BB. This work was supported by the National Science Centre, Poland (grant no. 2021/41/B/ST10/01086).