1. Oil drift modelling BE-AWARE II Final Conference, 18-19 November, Ronneby, Sweden Co-financed by the EU – Civil Protection Financial Instrument

2. Concept of modelling the development of an oil slick Oil drift modelling

3. Objective: How will a given spill will spread, drift, disperse: 1.For oil on surface and oil in the water column 2.For all spill location in the BA area 3.For all spill sizes 4.For all oil types 5.For all season 6.Include effects of oil spill recovery and chemical dispersion => several "infinities" of model-runs for each scenario Oil drift modelling

4. Method: Limit the calculations to a reasonable amount and still obtain a satisfying answer by conducting "Strategic oil spill modelling": including only necessary processes modelling with a sufficient accuracy sensitivity analyses, comparing with other models Difficulty is to judge: which processes and scenarios are necessary for the purpose when is the accuracy sufficient for the purpose Oil drift modelling

5. Process regimes: Oil on the ocean surface Chemically dispersed oil A 2x2 km grid 4 seasons, no sea ice Parameters: Sea temperature Frequency of wind velocity and direction Wave height (wind waves) Frequency of fog and mist The daily hours with sunlight Drift, spreading and fate

6. Oil types included Drift, spreading and fate TypeRepresentative substance 19Crude oil 20Fuel oil 21Gasoil, diesel, petroleum, jet fuel and light fuel oil 22Gasoline

7. Spill size classes Drift, spreading and fate Spill size classLower limit [t]Upper limit [t] Representative size [t] 0000.0 1010.3 21154.0 31530067.0 43005,0001,200.0 55,00015,0008,700.0 615,00050,00027,000.0 750,000150,00087,000.0

8. Spreading, resulting radius Slick area = Circle with radius R R'= Rgrav + Rtide+wind For the resulting area affected by a slick a radius R' is determined: 1.spreading by gravitation (radial spreading) 2.spreading by tide (ellipsoidal circulation) 3.and wind (superposition of wind drift)

9. Spreading, dispersion Chemical dispersion occurs after approx. 18 hrs (alarm, mobilisation, flight time, effect time): Phase1: Before application of dispersants (t < 18 hrs) Surface oil: R: Oil slick radius develops due to gravity Drift: as surface drift (Wind+current) Phase 2: After application of dispersants (t > 18 hrs) Dispersed oil: R:= R 0 +0.01x (based on observation of oceanic plumes) Radius increases 1/100 with downstream distance (tide effect included, not wind) Oil concentration based on plume depth := 30m Drift as for residual current (no wind effect)

10. Meteorological areas Based on wind statistics 3 speed classes 12 direction classes, 30° Drift Location F, Jan - Feb Wind speed class 1 Wind speed class 2 Wind speed class 3 Speed interval (m/s) 0.2 - 55 - 11>11 Representative wind speed (m/s) 3.5714

11. DRIFT Schematic illustration of resulting drift velocity (yellow) as a superposition of wind drift (light blue) and residual current drift (dark blue). Wind and current drift

12. Modelling the wind drift: Vdrift = 0,023 · W, W: Wind speed (m/s) Ddrift = D, D: Wind direction (deg) Drift

13. Hydrographical sub-regions Drift by wind and Residual currents (Mumm model input) Drift Meteorologi cal area Description Residual drift speed (m/s) Direction of drift (ºN) A West of Ireland0,0545 B NW of Scotland0,0745 C West of Norway0,145 D East of UK0,02150 E West of Denmark 0,0745 F Southern North Sea 0,01W, projected 30, 210 G English Channel 0,01W, projected 60, 240

14. Weathering and natural dispersion Volume of oil and water in oil emulsion on the sea surface (ITOPF, 2006). Group 1: diesel Group 2 & 3: light and heave crude oil Group 4: bunker oil

15. Simulation stop when 5% of the oil is left on the sea surface. The rest of the oil is either Weathered Floated on shore Drifted out of the model area over boundaries to the Atlantic Removed by response action Moddeling stop criteria

16. Verification on single specific spill Verification MUMM Oserit single spill

17. Effect of several selected spills SW-wind NW-wind Verification MUMM Oserit single spill

18. OSERIT: Specific time series BEAWARE: General statistics Verification MUMM Oserit multiple spill

19. Objective: Distribution of spilt oil after spreading, drift and weathering  All places (several hundreds)  spill sizes (7)  all oil types (4)  all winds (3 speeds and 12 directions)  all seasons (4) Summarising

20. Questions? Thank you beaware.bonnagreement.org