Dynamics of dense overflows – detailed studies from the Western Baltic Sea

Hans Burchard1, Hans Ulrich Lass1, Lars Umlauf1, Karsten Bolding2, Frank Janssen3, Volker Mohrholz1, Hannes Rennau1

1. Baltic Sea Research Institute Warnemünde

2. Bolding & Burchard Hydrodynamics3. Federal Maritime and Hydrographic Agency

hans.burchard@io-warnemuende.de

Oder: Wie Jürgen Sellschopp das Modellieren schätzen lernte.

Das kriegen die niemodelliert !

For the investigation of this problem, the international project cluster QuantAS(Quantification of water mass transformation processes in the Akona Sea) was set up.

Graphics: Jan Donath (IOW)

Photo: Frank Richter (Uni Rostock) © NDR

Uli Lass (2002):

„Wind turbine foundationsmay mix up dense bottom currents.“

Establishing the QuantAS Consortium in May 2003

...Treppenabsatzfoto Nr. 257 …

Interessantes Projekt auch aus der Sicht der FWG.

Wir könnten für Anfang 2004 mit Schiffszeit

dabei sein.

Baltic Sea bathymetry

Entire Baltic

Belt Sea / Western Baltic

Western Baltic Sea: Bathymetry

Darss Sill: 19 m

+

Drogden Sill: 8 m

+MARNET (IOW/BSH)

Farvandsvæsenet

baroclinic barotropic

Inflows over Drogden Sill

surface

bottom

Graphics: Frank Janssen (BSH)

Where does the Sound plume go ?

?

x

y

U-V

Dense bottom currents:

Balance between rotation,friction and pressure gradient

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• …

Lass die doch modellieren. Wir hocken lieber im

Container und pflegen unsere

Feldmessungen.

5 days

15 days

31 days

Sound lock-exchange experiment with GETM

Bottom salinity: 8 – 25 psu

Kann das denn

angehen ?

Searching for the plume

Plume coming down from the Sound (Feb‘ 2004)

Plume passing Kriegers Flak (Feb‘ 2004)

Profiles through plumenorth of Kriegers Flak

(Feb‘ 2004)

Realistic simulation of the Februar 2004 plume

Baltic Sea model:Baltic Sea MOM-3.1 model 3 nm horizontal resolution77 vertical (geopotential) grid layersMeteo forcing from ECWMF Reanalysis Project ERA40 (until August 2002)German Weather Service Global Model with a resolution (from September 2002).Boundary conditions stored for elevation, temperature and salinity at 57 deg 30‘ N (Kattegat) and 16 deg 30‘ E (east of Bornholm Sea)

Western Baltic Sea model: Sim-time: September 1, 2003 - May 1, 2004Forced by German Weather Service Local Model (resolution: 7 km and 3 hours)Lateral boundary conditions from Baltic Sea model Resolution: 1/2 nm in the horizontal, 50 general vertical coordinate layersTime step was 10 s for barotropic and 300 s for baroclinic mode.

Domain decomposition for Western Baltic Sea model

Bottom salinity in Arkona Sea

Salt transport across Drogden Sill

Model validation: Darss Sill

Model validation: Arkona Buoy

Feb. 2004 section

across Kriegers Flak

November 2005: More detailed QuantAS observations

Nov 2005: Velocity structure of dense bottom current

Ship A:TL-ADCP

Ship B: Microstructure

View

1 km

Flow

Eastcomp.

Northcomp.

Can we explain the flow structure ?

T2:Turbulence Measurements

enhanced turbulencein down-welling region

interfacial turbulence

quiet core

BBL Turbulence

21

3

N

Lo

Ozmidov Scale:

Ozmidov Scale

Dissipation Rate

GETM 2DV Slice Model: Transverse gravity current structure

Na, Jürgen, war das nicht ne schöne Zeit,

damals 03 – 07 ?Ach ja … und

aus dem Modell konnte man ja so richtig was

lernen …

… dann kann ich

ja in Rente

gehen …