SHI-YONG YU GeoBiosphere Science Centre Department of Geology/Quaternary Sciences

1. The Littorina transgression in southeastern Sweden and its relation to mid-Holocene climate variability SHI-YONG YU GeoBiosphere Science Centre Department of Geology/Quaternary Sciences Lund University Sölvegatan 12 SE-223 62 LUND Supervisors P. Sandgren, B. E. Berglund and L. Barnekow

2. What are sea-level changes? • Sea level is the location where ocean water intercepts the land • Sea-level changes are the result of the complex feedback among the Earth’s different spheres at variable response time scales Sabadini, 2002

3. Future sea-level rise: an enigma • Sea-level history over the last 100 years was well recorded by tide gauges (2 mm/yr). • An acceleration was observed over the last decade (3 mm/yr). • Other components involved in this complex pattern are unclear. Cabanes et al., 2001 Munk, 2002

4. The best prophet of the future is the past To give a credible scenario of future sea-level rise, go back to the past to look at sea level adaptations to climate changes under similar boundary conditions to the present.

5. The Littorina transgression: A best analogue to the present sea-level rise The Littorina transgression (8500-3000 cal. BP) is a manifestation of Baltic Sea level rise in response to the pronounced drawdown of global ice volume • Warming climate (the mid-Holocene thermal maximum) • Soar of greenhouse gases (e.g. CO2, CH4) level • Absence of major continent ice sheets Littorina littorea Linné

6. The Littorina transgression - hypotheses and causes One main transgression (the Finnish view)Caused by the uniform eustatic rise of global sea level Several minor transgression waves (the Danish-Swedish view)Caused by changing global ice volume and regional climate conditions

7. Climate changed, so did Baltic Sea level Evidence from both ice cores and deep-sea sediments reveal that the North Atlantic area has experienced millennial-scale climate changes. Beach ridge, Olsäng (Mikaelsson, 1978)

8. Beach ridges, Inlängan island (Photo: Berglund, 1964)

9. Beach ridges on Inlängan and Aspö islands (Berglund, 1964)

10. Isolation lakes and lagoons: excellent benchmarks of past sea level Dating the isolation/contact of the basins may provide a powerful constraint on relative sea-level changes

11. Smygen lagoon (Photo: Berglund, 2000)

12. Smygen: -1 m Hunnemara: 3 m Ryssjön: 4.5 m Färsksjön: 7.2 m (the highest lake containing brackish sediments in Blekinge)

13. Fieldwork (Photo: Berglund, 2000)

14. Flowchart of lab analyses

15. 1st story First order sea-level changes: Eustasy vs. isostasy A big thaw of the Antarctic Ice Sheet

16. Coastal basins: Precise sea-level “index points”

17. A changing ice volume? The Littorina transgression is caused by a continuous ice-volume-equivalent sea-level rise, interspersed with variable rates

18. Global climate during the “Noah’s Flood” • Storegga tsunami (Andrén, 2001)? • Slow down of crustal rebound? • Laurentide floods (Tooley, 1989)? • A global meltwater pulse 8000 years ago • Rapid depletion of seawater d18O • A IRD spike in the South Atlantic (Hodell et al., 2001) • Flooding in Chesapeake Bay/8000 cal. BP (Bratton et al., 2003) • A break of coral growth in the Caribbean area (Blanchon and Shaw, 1995) • Black Sea transgression

19. 2nd story Linking Baltic Sea-level fluctuations to North Atlantic storminess at millennial time scale Coastal dune, W Denmark (Photo: Yu, 2003)

20. Dating sea-level-sensitive floras (e.g. dinoflagellates, diatoms, seagrasses, stoneworts) provides evidence for millennial-scale sea-level changes

21. 3rd story Centennial-scale sea-level changes: A window to the NAO past?

23. Sea-level changes: Cycle, cycle all the time? The 480-yr cycle: tidal origin? 480*2=960 yr 480*3=1440 yr the enigmatic 1500 yr cycle was solved! Wavelet and power spectral transforms of a macrofossil series from Lake Ryssjön

24. Conclusions • The Littorina transgression in southeastern Sweden covers the time span 8500–3000 cal. BP. It can be ascribed to the accelerated rise of global sea level, overprinting the slow isostatic uplift in southern Scandinavia during the middle Holocene. • Within the Littorina Sea phase, five minor transgressions are recorded: L1 8500–8200, L2 7800–6900, L3 6400–5600, L4 5300–4700, and L5 4500–4100 cal. BP. These minor transgressions, lasting 500–1000 years in the study sites, occurred almost synchronously across the southern Baltic Sea. • The first transgression (L1) can be linked to the flood of the proglacial lakes in North America. The most pronounced transgression (L2) is marked by a Baltic Sea level rise by ca. 8 m in 500 years, at an accelerated rate of ~15 mm yr-1. It suggests a global meltwater pulse probably triggered by the partial collapse of the Antarctic Ice Sheet.

25. The younger minor transgressions were possibly caused by ice-volume changes in combination with submillennial-scale variations in regional storminess. • Centennial-scale sea-level fluctuations show good coherence with ice-core sea-salt ions and cosmogenic nuclides in some time windows, suggesting solar forcing probably through a system similar to the dipole oscillation of the North Atlantic atmosphere (i.e. NAO). In addition, tidal actions related to lunar cycles may exert another important influence on Baltic Sea level during the middle Holocene.

26. Thank you!