Hans Burchard, Frank Janssen, Hans Ulrich Lass, Volker Mohrholz, Hannes Rennau, and Lars Umlauf Leibniz Institute for Baltic Sea Research Warnemünde, Germany Internal technical support: Toralf Heene, Günter Plüschke, Dietmar Rüss, Ingo Schuffenhauer External scientific collaboration: Lars Arneborg, Karsten Bolding, Volker Fiekas, Frank Gerdes, Michaela Knoll, Hartmut Prandke, Jürgen Sellschopp Status of the QuantAS-Off regional scale dynamical studies

Kriegers Flak Motivation: wind farms in the Western Baltic Sea

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

baroclinicbarotropic Inflows over Drogden Sill surface bottom Source: Farvandsvæsenet

Where does the Sound plume go ? ?

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., 2005

Plume passing Kriegers Flak (Feb 2004) Burchard et al., 2005 For more details, see Sellschopp et al., 2006

Baltic Sea vertical mixing processes How would offshore wind farm foundations affect this ? Reissmann et al., 2007

Role of vertical mixing for the Baltic Sea ecosystem

GETM Western Baltic Sea hindcast Burchard et al, 2007

GETM Western Baltic Sea hindcast

Model validation: Darss Sill Burchard et al, 2007

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., 2007 Arneborg et al., 2007: Entrainment laws for each location

GETM 2DV Slice Model: Transverse gravity current structure Umlauf et al., in prep.

QuantAS – Quantification of water mass transformations in the Arkona Sea Time series stations Mohrholz et al., in prep.

QuantAS – Quantification of water mass transformations in the Arkona Sea Moored devices Kriegers Flak North Kriegers Flak South Mohrholz et al., in prep.

QuantAS – Quantification of water mass transformations in the Arkona Sea Salinity time series Mohrholz et al., in prep.

QuantAS – Quantification of water mass transformations in the Arkona Sea Cross channel transect : :49 UTC Along channel transect : :39 UTC Inflowing plume north of Kriegers Flak Mohrholz et al., in prep.

Hydrography at Bornholmsgat QUANTAS – ADP structure function approach Mohrholz et al., in prep.

Transverse structure in Bornholm Channel Reissmann et al., 2007

Model derived monthly mean vertically integrated physically and numerically induced salinity mixing Physical mixing Numerical mixing Burchard et al., 2007; Burchard and Rennau, 2007; Rennau et al., in prep.

Signature of piles Current Salzgehalt Temperatur Mixing by bridge Mixing at the piles of the Western Great Belt Bridge Lass et al., submitted

CTD chain tows at Western Great Belt Bridge Lass et al., submitted upstreamdownstream

Basic parameterisation for friction due to structures in water Additional production of turbulence: Friction coefficient:

QuantAS-IOW-Publications Burchard, H., H.U. Lass, V. Mohrholz, L. Umlauf, J. Sellschopp, V. Fiekas, K. Bolding, and L. Arneborg, "Dynamics of medium-intensity dense water plumes in the Arkona Sea", Western Baltic Sea, Ocean Dynamics, 55, , Sellschopp, J., L. Arneborg, M. Knoll, V. Fiekas, F. Gerdes, H. Burchard, H. U. Lass, V. Mohrholz, L. Umlauf, "Direct observations of a medium-intensity inflow into the Baltic Sea", Cont. Shelf Res., 26, , Arneborg, L., V. Fiekas, L. Umlauf, and H. Burchard, "Gravity current dynamics and entrainment - a process study based on observations in the Arkona Sea", J. Phys. Oceanogr., 37, , Umlauf, L., L. Arneborg, H. Burchard, V. Fiekas, H.U. Lass, V. Mohrholz, and H. Prandke, The transverse structure of turbulence in a rotating gravity current, Geophys. Res. Lett., 34, L08601, doi: /2007GL029521, Mohrholz, V., H. Prandke and H. U. Lass, Estimation of TKE dissipation rates in dense bottom plumes using a Pulse Coherent Acoustic Doppler Profiler (PC-ADP) - Structure function approach, J. Mar. Sys., accepted for publication. Burchard, H., F. Janssen, K. Bolding, L. Umlauf, and H. Rennau, Model simulations of dense bottom currents in the Western Baltic Sea, Cont. Shelf Res., accepted for publication. Burchard, H., and H. Rennau, Comparative quantification of physically and numerically induced mixing in ocean models, Ocean Modelling, accepted for publication. Reissmann, J., H. Burchard, R. Feistel, E. Hagen, H.U. Lass, V. Mohrholz, G. Nausch, L. Umlauf, and G. Wieczorek, State-of-the-art review on vertical mixing in the Baltic Sea and consequences for eutrophication, Progr. Oceanogr., accepted for publication. Lass, H.U., V. Mohrholz, M. Knoll, and H. Prandke, "On the impact of a pile on a moving stratified flow", Cont. Shelf Res., submitted.

Conclusions: The inflow dynamics of the Arkona Sea are far more complex than assumed before. Specifically the role of Earth rotation for entrainment had been underestimated before. Next steps: Calibration of the friction parameterisation by means of the lab experiments, the RANS experiments and the Great Belt Bridge field observations. Various numerical experiments without and with the parameterisation of different wind farm locations and abundances in the Arkona Sea. Evaluation of the wind farm effects and general recommendations for future wind farm locations.