Alar Rosentau

Palaeogeographic Model for the SW Estonian Coastal Zone of the Baltic Sea

The authors combined geological, geodetic and archaeological shore displacement evidence to create a temporal and spatial water-level change model for the SW Estonian coast of the Baltic Sea since 13,300 cal. years BP. The Baltic Sea shoreline database for Estonian territory was used for the modelling work and contained about 1,200 sites from the Baltic Ice Lake, Ancylus Lake and Littorina Sea stages. This database was combined with a shore displacement curve from the Parnu area (in SW Estonia) and with geodetic relative sea-level data for the last century. The curve was reconstructed on the basis of palaeocoastline elevations and radiocarbon-dated peat and soil sequences and ecofacts from archaeological sites recording three regressive phases of the past Baltic Sea, interrupted by Ancylus Lake and Littorina Sea transgressions with magnitudes of 12 and 10 m, respectively. A water-level change model was applied together with a digital terrain model in order to reconstruct coastline change in the region and to examine the relationships between coastline change and displacement of the Stone Age human settlements that moved in connection with transgressions and regressions on the shifting coastline of the Baltic Sea.

Comparing different post-IR IRSL approaches for the dating of Holocene coastal foredunes from Ruhnu Island, Estonia

Different post-IR Infrared Stimulated Luminescence (IRSL) approaches are applied to sediments from a Holocene coastal foredune sequence on Ruhnu Island in the eastern Baltic Sea. The comparison of De-values and ages determined by the different approaches is complimented by fading and bleaching experiments. The fading experiments imply strong fading of IRSL (50°C) signals and no fading of any of the post-IR IRSL signals, but this is not confirmed by the determined De-values. In fact, post-IR IRSL (150°C) De-values agree within errors with those calculated for IRSL (50°C). From the bleaching experiments it is inferred that the higher values observed for post-IR IRSL at more elevated stimulation temperatures (225°C/290°C) are likely related to either thermal transfer and/or slow-to-bleach components within the signal. For the dating of the Holocene foredune sequence of Ruhnu Island, the post-IR IRSL (150°C) approach is preferred and these agree with the limited independent age control available from radiocarbon dating. Accordingly, the sequence formed between ca. 7.0 ka and 2.5 ka ago.

Palaeoreconstruction of the Baltic Ice Lake in the Eastern Baltic

A GIS-based palaeogeographic reconstruction of the development of the Baltic Ice Lake (BIL) in the eastern Baltic during the deglaciation of the Scandinavian Ice Sheet is presented. A Late Glacial shoreline database containing sites from Finland, NW Russia, Estonia, Latvia and modern digital terrain models was used for palaeoreconstructions. The study shows that at about 13,300 cal. years BP the BIL extended to the ice-free areas of Latvia, Estonia and NW Russia, represented by the highest shoreline in this region. Reconstructions demonstrate that BIL initially had the same water level as the Glacial Lakes Peipsi and Vortsjarv because these water bodies were connected via strait systems in central and northeast Estonia. These strait systems were gradually closed at about 12,700–11,700 cal. years BP due to isostatic uplift, prior to the final drainage of the BIL. Glacial Lake Vortsjarv isolated from the BIL at about 12,400–12,000 cal. years BP. Exact timing of Glacial Lake Peipsi isolation is not clear, but according to the altitude of the threshold in northeast Estonia and shore displacement data, it was completed at about 12,400–11,700 cal. years BP.

Sea level changes and Neolithic hunter-fisher-gatherers in the centre of Tallinn, southern coast of the Gulf of Finland, Baltic Sea

Relative sea level (RSL) changes and the palaeogeography of a Neolithic hunter-fisher-gatherer settlement site on the former shore of the Gulf of Finland in the city centre of Tallinn were reconstructed by implementing GIS in landscape modelling based on archaeological, sedimentary and shore displacement data. AMS radiocarbon dating of mammal bones from the cultural layer suggests the existence of the hunter-fisher-gatherer settlement around 5.1–4.8 cal. ka BP on a seaward inclining sandy beach of Tallinn palaeo-bay c. 100 m from the Litorina Sea shoreline and at about 2.4 m above the coeval sea level. The shoreline passed the study site at about 5.8 cal. ka BP and retreated towards northeast with an average speed of 13 m per century, while the RSL lowered by c. 2.5 mm annually. Combining radiocarbon dates of terrestrial and marine mammal bones from the Neolithic cultural layer, a marine reservoir effect of 350 14C years for the brackish-water Baltic Sea was calculated. By using high-resolution archaeological data in combination with RSL and other geological proxies, we demonstrate new possibilities to reconstruct the palaeoenvironment of deeply buried coastal settlement sites and to predict a possible continuation of the cultural layer in heavily built-up areas.

Sea-Level Change and Flood Risks at Estonian Coastal Zone

This paper reviews Estonian relative sea level, land uplift and coastal floods data and provides sea-level scenarios and risk assessment of coastal flooding in urban areas for the twenty-first century. Considering the present post-glacial land uplift rates of Estonian coastal areas and the global ocean level rise projections, the long-existing trend of relative sea-level lowering may very probably be replaced by a relative sea-level rising trend during the twenty-first century. By the end of the twenty-first century we project the relative sea level to be c. 20 to 40 cm or c. 40 to 60 cm higher in the case of the International Panel for Climate Change Representative Concentration Pathways (RCP) 4.5 or RCP 8.5 scenario, respectively. The sea-level rise together with the increased storm frequency and decreased winter ice cover period will very probably increase the extent of floods during the twenty-first century. A significant coastal flooding risk affects four cities, Parnu, Kuressaare, Haapsalu and Tallinn and eight smaller towns. The largest coastal flooding in Estonia is recorded in Parnu, with the highest sea level 275 cm in 2005. Calculations show that due to the impact of predicted climate change and in the case of certain weather conditions, coastal floods in Parnu may affect areas up to 400 cm above the present sea level by the end of the twenty-first century. The scenarious of future flood limits are needed for sustainable planning of the coastal zone and for development of rescue strategies.There are already several land use and urban planning instruments and laws for climate adaptation, such as environmental impact assessment, risk assessment and restriction zones for construction in certain buffer and flood areas. Flooding risk measures consist of risk mapping and a national emergency plan. However, further integration of climate issues into existing laws, strategies and land use plans is essential to have a targeted approach in reducing the vulnerability of populated areas and strengthening the adaptive capacity of the urban system against climate change.