Holocene palaeoenvironment of the central Baltic Sea based on sediment records from the Gotland Basin

Abstract

Sediment archives are the key source of information about long-term environmental dynamics under changing climate conditions, which is crucial for reliable forecasts. The presented work aims at reconstructing the Baltic Sea palaeoenvironment during the Littorina stage with a particular interest in variations in the saline water inflows. Complex analysis (including geochemical and micropalaeontological studies) of sediment sequences, obtained in the Eastern Gotland Basin, was performed. According to the radiocarbon dating results, the combined sediment record covers the last c. 7 cal ka BP. During this time, increased inflow activity was recorded in the Holocene Thermal Maximum, the Roman Warm Period, and Dark Ages. The predominantly positive phase of NAO during these periods resulted in the prevalence of westerly winds over the Baltic region, which in turn led to more frequent inflows of North Sea waters. The decrease in the frequency of inflows during the Little Ice Age and the Modern Warm Period coincides with the negative phase of NAO and weaker westerlies. The periods of the warmer climate, characterised by an increase in surface water productivity, correspond to the Holocene Thermal Maximum, the Roman Warm Period, the Medieval Climate Anomaly, and the Modern Warm Period. Due to the relatively shallow position, the coring site was not affected by hypoxia during the latter warm periods.