Observations and simulations of a salt water intrusion into the Arkona Sea

Transcription

1 Observations and simulations of a salt water intrusion into the Arkona 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 Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 1/28

2 Contents Projected Offshore Wind parks in the Arkona Sea QuantAS consortium QuantAS-Off project Idealised model simulations for the Arkona Sea Observations of medium strength inflow event Data - model intercomparisons Research questions Discussion: Will there be any extra mixing??? Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 2/28

3 Offshore wind farms According to a 22 strategy paper of the German Ministry for Environment, renewable energies will be massively extended in Germany. One of the major generation principles will be wind turbines. Since space on land is already nearly exhausted, offshore wind farms are projected in the German EEZ (North Sea and Baltic Sea). Ecological aspects must be considered. The BSH is responsible for the approvals of erection, operation and use of offshore wind farms. Here, potential ecological impacts of these constructions will be studied. Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 3/28

4 The German perspective... Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 4/28

5 All problems considered? Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 5/28

6 Offshore wind farms Problem as formulated by Uli Lass (IOW) in 22: The foundations of offshore wind turbines could lead to increased entainment of ambient water into medium strength dense bottom plumes flowing through the Arkona Sea. This could lead to decreased ventilation of the halocline in the Bornholm Basin and other Baltic Sea basins. Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 6/28

7 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. Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 7/28

8 QuantAS-Off Project QuantAS-Off (QuantAS Impact of Offshore Wind Farms, 24-27) will deal with the physical impact of wind turbine foundations. Cooperation: 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. Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 8/28

9 Pathway of medium inflows? Period / duration: Impact: 5 per winter for 1 week Ventilation of halocline in Baltic Sea Graphics by Toralf Heene (IOW) Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 9/28

10 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. Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 1/28

11 Idealised simulation Bottom salinity after 5 days 56 Latitude 55 S / psu Longitude Simulation with GETM Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 11/28

12 Idealised simulation Bottom salinity after 15 days 56 Latitude 55 S / psu Longitude Simulation with GETM Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 12/28

13 Idealised simulation Bottom salinity after 3 days 56 Latitude 55 S / psu Longitude Simulation with GETM Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 13/28

14 Idealised simulation Surface salinity after 3 days 56 S / psu Latitude Longitude Simulation with GETM Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 14/28

15 FWG cruise From January 26 to February 13, 24, FWG Kiel organised a research cruise into the Arkona Sea. Luckily, an inflow event occurred during this period. Q / km 3 Accumulated flux over Drogden Sill 5 accum. flux /1 11/1 21/1 31/1 1/2 2/2 Date in 24 Calculated from sea level differences according to Jakobsen et al. [1997] Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 15/28

16 Observed & simulated plume South-north section south of Drogden Sill Depth -2 Observed plume on Feb 1 (salinity) S/psu Depth Simulated plume after 7 days (salinity) S/psu Latitude Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 16/28

17 QuantAS: Inflow (observed) ADCP in the ship's well. Bottom layer affected 28 Jan 24by bottom interaction 8:3 -of 12:3 sound beam side lobes. Velocity in the plume in excess of.5 m/s. 1 Feb 24 16:2-2:5 Observations & Graphics by Jürgen Sellschopp & Michaela Knoll (FWG Kiel) Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 17/28

18 QuantAS: Simulated currents Plume after 7 days (eastward velocity) u/m s 1.6 Depth Latitude Depth -2 Plume after 7 days (northward velocity) v/m s Latitude Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 18/28

19 Observed & simulated plume South-north section south of Drogden Sill Depth -2 Observed plume on Feb 2 (salinity) S/psu Depth Simulated plume after 9 days (salinity) S/psu Latitude Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 19/28

20 QuantAS: Inflow (observed) Progressing plume 2 Feb 24 1:2-14:5 18 hours later the salinity plume arrives at 55 1' N. The estimated velocity of the salinity front is 1 cm/s. The salt water supply has momentarily ceased. Observations & Graphics by Jürgen Sellschopp & Michaela Knoll (FWG Kiel) Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 2/28

21 QuantAS: Simulated currents Plume after 9 days (eastward velocity) u/m s 1.6 Depth Latitude Depth -2 Plume after 9 days (northward velocity) v/m s Latitude Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 21/28

22 Observed & simulated plume South-north section across Kriegers Shoal Observed plume on Feb 5 (salinity) Depth S/psu Simulated plume after 3 days (salinity) Depth S/psu Latitude Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 22/28

23 QuantAS: Inflow (observed) Branches west and north of Krieger s Shoal 5 Feb 24 1:45-15:31 Observations & Graphics by Jürgen Sellschopp & Michaela Knoll (FWG Kiel) Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 23/28

24 QuantAS: Simulated currents Eastward velocity in quasi-steady state Depth -2-3 u/m s Depth Latitude Northward velocity in quasi-steady state Latitude v/m s 1.2 Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 24/28

25 24-hour station data Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 25/28

26 Observed & simulated profiles Position: North of Kriegers Shoal Observed salinity S Simulated salinity S -5-5 z / m z / m S / psu S / psu Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 26/28

27 Observed & simulated profiles Position: North of Kriegers Shoal Observed velocity u v Simulated velocity u v -5-5 z / m z / m u,v / m s 1 u,v / m s 1 Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 27/28

28 Research Questions QuantAS tries to answer the following questions: Which are the major mixing mechanisms for Baltic Sea inflow events. Can we quantify those by combining observations with numerical models? Is there extra mixing due to offshore wind turbines? See energy budget calculation.) How does increased mixing in the Arkona Sea affect the Baltic Sea ecosystem? Is additional vertical mixing due to projected offshore wind farms significant? Seminar of the Department for Physical Oceanography and Instrumentation, IOW, Warnemünde, Germany, Nov. 2, 24. p. 28/28