Dynamics of medium-intensity dense water plumes in the Arkona Basin, Western Baltic Sea

Transcription

1 Dynamics of medium-intensity dense water plumes in the Arkona Basin, Western Baltic Sea Hans Burchard 1,3, Hans Ulrich Lass 1, Volker Mohrholz 1, Lars Umlauf 1, Jürgen Sellschopp 2, Volker Fiekas 2, Karsten Bolding 3, and Lars Arneborg 4 hans.burchard@io-warnemuende.de 1. Baltic Sea Research Institute Warnemünde, Germany 2. FWG Kiel, Germany 3. Bolding & Burchard Hydrodynamics, Asperup, Denmark 4. Dept. of Oceanography, Göteborg University, Sweden Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 1/22

2 Contents Description of idealised simulation with GETM. Model results for idealised inflow. Comparison of simulation with observational data. Future work. Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 2/22

3 Arkona Sea map Map with observational sections and stations and model transects Drogden Sill Bornholm Basin 55.4 Bornholmgatt 55.2 Latitude [deg North] Fehmarn Belt Darss Sill Kriegers Flak Arkona Basin Pomeranian Bight [m] Longitude [deg East] Red & purple: ship tracks; green: model transects; diamond: station Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 3/22

4 Simulation with GETM Idealised simulations with the General Estuarine Transport Model (GETM) are carried out for the Arkona Sea. Some specifications: Backround salinity: 8 psu, salinity at inflow: 25 psu. Sea level elevated by 2 cm at inflow boundary. Constant wind from south-west. 1/2 nm horizontal resolution. Bottom-fitted general vertical coordinates with 25 layers. One month simulation time until quasi-steady state. Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 4/22

5 Idealised simulation Bottom salinity after 5 days 56 Latitude 55 S / psu Longitude Simulation with GETM Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 5/22

6 Idealised simulation Bottom salinity after 15 days 56 Latitude 55 S / psu Longitude Simulation with GETM Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 6/22

7 Idealised simulation Bottom salinity after 3 days 56 Latitude 55 S / psu Longitude Simulation with GETM Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 7/22

8 Idealised simulation Surface salinity after 3 days 56 S / psu Latitude Longitude Simulation with GETM Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 8/22

9 FWG cruise Water mass flux and current velocity during FWG cruise (Jan 26 to Feb 13, 24): Q / km 3 v / (m s 1 ) 5 Accumulated flux over Drogden Sill accum. flux /1 11/1 21/1 31/1 1/2 2/ Southward current velocity ADCP /1 11/1 21/1 31/1 1/2 2/2 Date in 24 Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 9/22

10 Observed & simulated plume South-north section south of Drogden Sill -1-2 Observed plume on Feb 1 (salinity) S/psu Simulated plume after 7 days (salinity) S/psu Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 1/22

11 Observed & simulated plume South-north section south of Drogden Sill Plume on Feb 1 (northward velocity) v/(m s 1 ) Plume after 8 days (northward velocity) v/(m s 1 ) Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 11/22

12 Observed & simulated plume South-north section south of Drogden Sill -1-2 Observed plume on Feb 2 (salinity) S/psu Simulated plume after 9 days (salinity) S/psu Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 12/22

13 Observed & simulated plume South-north section south of Drogden Sill Plume on Feb 2 (northward velocity) v/(m s 1 ) Plume after 9 days (northward velocity) v/(m s 1 ) Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 13/22

14 Observed & simulated plume South-north section across Kriegers Shoal Observed plume on Feb 5 (salinity) S/psu Simulated plume after 3 days (salinity) S/psu Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 14/22

15 Observed & simulated plume South-north section across Kriegers Shoal Section on Feb 5 (eastward velocity) u/(m s 1 ) Eastward velocity in quasi-steady state u/(m s 1 ) Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 15/22

16 Observed & simulated plume Bottom salinity from observations and idealised model simulation together with bottom topography Bottom salinity and water depth depth S from model S from observation 3 depth, salinity Latitude Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 16/22

17 24-hour station data Lars Arneborg & Hans Burchard operating the microstructure profiler by hand. Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 17/22

18 Observed & simulated profiles Position: North of Kriegers Shoal Observed salinity S Simulated salinity S z / m z / m S / psu S / psu Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 18/22

19 Observed & simulated profiles Position: North of Kriegers Shoal Observed velocity u v Simulated velocity u v z / m z / m u,v / m s 1 u,v / m s 1 Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 19/22

20 QuantAS Consortium The international consortium QuantAS (Quantification of water mass transformation processes in the Arkona Sea) has been built to discuss questions of natural and anthropogenic mixing in the Arkona Sea. Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 2/22

21 QuantAS-Off Project QuantAS-Off (QuantAS Impact of Offshore Wind Farms, 24-27, funding by German Federal Environment Ministry) will deal with the physical impact of wind turbine foundations. University of Rostock, Fluid Mechanics Institute: small-scale laboratory experiments University of Hanover, Fluid Mechanics Institute: small-scale modelling studies Baltic Sea Research Institute Warnemünde: Coordination, in-situ observations, regional scale modelling, synthesis Major aim: Give recommendations where and where not to build offshore wind farms. Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 21/22

22 Future Research Questions The projects QuantAS-Off and QuantAS-Nat (25-28, German Reserch Foundation) will try to answer the following upcoming questions: Which are the major mixing mechanisms for Baltic Sea inflow events. Can we quantify those by combining observations with numerical models? How strong is the numerical mixing of the model? How does increased mixing in the Arkona Sea affect the Baltic Sea ecosystem? How strong can the additional vertical mixing due to projected offshore wind farms be? Baltic Sea Science Conference, Sopot, Poland, June 21, 25 p. 22/22