Sea-Level Change in the Baltic Sea

ABSTRACT The development of the Baltic Sea during the Holocene was mainly controlled by climatically driven eustatic sea-level change and vertical crustal movements. Both factors affect sea-level changes interpreted from sedimentological investigations at coastal locations. Comparison of relative sea-level curves with a eustatic curve reveals the contribution of vertical crustal movements to coastal changes as expressed via a “coast index.” A coast index c(i) for the Baltic region can be derived, by which a location can be allocated to either a “crustal-uplift/subsidence type” or a “climate-controlled type.” Coastal locations investigated along the Fennoscandian Shield belong to the crustal-uplift type and locations along the southern and southwestern coast belong to the climate-controlled type, regardless of whether they are on the East European Platform or the West European Platform. Data on recent vertical crustal movements show a broad, predominantly subsiding zone between the rising blocks of Scandinavia (glacio-isostatic uplift) and the Carpathians (northward drift of the African Plate) to the west of the Tornquist-Teisseyre Zone (TTZ). Movements may additionally be influenced by processes initiated along the North Atlantic Mid-Ocean Ridge. The subsiding belt contiguous to the Fennoscandian Shield is interpreted as a collapsing as- thenospheric bulge originally surrounding the Pleistocene ice shield. The analysis of relative sea-level changes leads to the assumption that the process of collapse reached a steady state during the Late Litorina Stage. Crustal movement data, together with data from modeling of future sea-level change, can be used for calculating scenarios of relative sea-level development, providing a background for long-term planning of human activities in coastal areas.