Centennial-scale cycles in middle Holocene sea level along the southeastern Swedish Baltic coast

• Published in: Geological Society of America Bulletin
• Main Author: Yu, Shiyong
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Society of America 2003
• Subjects: Geology; NAO; Baltic sea-level changes; middle Holocene storminess; forcing; solar; lunar cycle; North Atlantic; North Atlantic oscillation
• Online Access: https://lup.lub.lu.se/record/296104; https://doi.org/10.1130/B25217.1

Submerged sea grasses and stoneworts growing in the immediate nearshore of the Baltic Sea are sensitive indicators of sea level. The alternating changes in concentrations of sea grass and stonewort macrofossils, obtained from an ancient lagoon of the Baltic Sea, are ascribed to middle Holocene sea-level fluctuations along the southeastern Swedish coast. Abundances of stonewort and sea grass macrofossils between 7500 and 6000 cal. (calibrated) yr B.P. were lower and less variable, indicating high and relatively stable sea level. Low-frequency fluctuations of sea level with a 1470 yr period during this time may have been forced by tidal action in the millennial band. After 6000 cal. yr B.P., sea level was lower and exhibited strong fluctuations at centennial time scales, as evident in the stonewort and sea grass macrofossil records. Such a high-frequency oscillatory mode of sea level may have been regulated by centennial-scale solar activities or tidal actions, or both. The modest variation in solar irradiance is unlikely to have resulted in large-scale oscillations of sea level by directly changing the steric component. Instead, it governed sea-level fluctuations by changing the regional storminess through a North Atlantic Oscillation (NAO)-like system. Storms embedded in the NAO-induced southwesterly winds played a major role in the centennial-scale fluctuations of the Baltic Sea level by pushing saltwater from the North Sea into the Baltic basin.