1. Hans Burchard Baltic Sea Research Institute Warnemünde, Germany hans.burchard@io-warnemuende.de The invisible extremes: The dynamics of Baltic Sea inflow events

2. Let us first have a look into the observed long-term surface salinity in the Central Baltic Sea

3. Sea surface salinity in the Central Baltic Sea Feistel et al., 2006 How to attribute this to a certain process ?

4. Bottom salinity in the Central Baltic Sea Feistel et al., 2006

5. A century of salinity in the Central Baltic Sea Graphics: Courtesy to Markus Meier

8. All inflows have to pass the Western Baltic Sea

9. Western Baltic Sea monitoring stations Darss Sill: 19 m + Drogden Sill: 8 m + MARNET (IOW/BSH) Farvandsvæsenet Arkona Sea: 48 m +

10. Three types of Baltic Sea inflow events: Major Baltic inflows – barotropic (wind driven) Strong Baltic inflows – baroclinic (density driven) Medium Baltic inflows – mixed (typically through Sound)

11. Baltic Inflows over Darss Sill: the year 2003 Major barotropic inflow Strong baroclinic inflow Source: IOW

12. baroclinic barotropic Inflows over Drogden Sill (through Sound) surface bottom Graphics: Frank Janssen (BSH)

13. Where does the Sound plume go ? ?

14. GETM is a 3D numerical model for estuarine, coastal and shelf sea hydrodynamics with applications to the Tidal Elbe Wadden Sea Limfjord Lake of Geneva, Western Baltic Sea, North Sea – Baltic Sea system …

15. 5 days 15 days 31 days Sound lock-exchange experiment with GETM Main plume goes via north of Kriegers Flak: Is this real ? Bottom salinity: 8 – 25 psu Burchard et al., OD, 2005.

16. Plume passing Kriegers Flak (Feb 2004) Burchard et al., OD, 2005.

17. Inflows north of Kriegers Flak

18. GETM Western Baltic Sea hindcast

21. Model validation: Darss Sill

22. Model derived monthly mean vertically integrated physically and numerically induced salinity variance decay Physical mixing Numerical mixing Burchard et al., 2007 (submitted), Burchard and Rennau, 2007 (submitted)

23. Nov 2005: Velocity structure of dense bottom current Ship A: TL-ADCP Ship B: Microstructure View 1 km Flow East comp. North comp. Can we explain the flow structure ? Umlauf et al., GRL, 2007

24. GETM 2DV Slice Model: Transverse gravity current structure

25. Conclusion: Even after decades of intensive Baltic Sea research, there are still many miracles to be understood. The major physical process question is: How does the Baltic Sea overturn work ? This includes the understanding of the entire pathway (in time and space) of water and its contents from entering to exiting the Baltic Sea.