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Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde

Coastal Ocean Dynamics Second course: North Sea dynamics. Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde hans.burchard@io-warnemuende.de. North Sea bathymetry. Source: Werner Alpers. North Sea catchment areas and Exclusive Economic Zones. Weser. Elbe.

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Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde

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  1. Coastal Ocean Dynamics Secondcourse: North Sea dynamics Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde hans.burchard@io-warnemuende.de

  2. North Sea bathymetry Source: Werner Alpers

  3. North Sea catchmentareas and ExclusiveEconomicZones Weser Elbe Rhine Source: OSPAR Commission

  4. Annual cycleofseasurfacetemperature in North Sea

  5. Generation ofthe semi-diurnal lunar (M2) tide http://www2.astro.psu.edu/users/cpalma/astro10/class21.html

  6. Generation ofthe semi-diurnal solar (S2) tide http://www2.astro.psu.edu/users/cpalma/astro10/class21.html

  7. Tidalchartforthe M2tide (phaselines) http://en.wikipedia.org/wiki/Amphidromic_point

  8. Why do thetides in the North Sealooklikethis ? Tidalwavesenterinto North Seathrough northern boundaryand English Channel. Phase propagationis c = (g * depth)1/2, g = 9.81 m/s2 (depth = 40 m  c = 20 m/s = 72 km/h) Due to Earth rotation, tidalwavesare Kelvin waves, leaning on a coasttotheright. Energyloss due tobedfriction: tidalwavesloose power duringtheirjourneythroughthe North Sea.

  9. Tidalchart forthe M2tide fulllines: amplitude dashed: phase (Source: POL)

  10. Tidalchartforthe M2tide (phaselines)

  11. Amphidromicpoint M2tidalchartof Southern North Sea Prandle, 1981

  12. Tidalpropagationintothe Baltic Seaisblocked !

  13. Tides in theWaddenSea (asseen in 200 m resolution model)

  14. WaddenSea model: M4tidalelevations (phaseandamplitude) asvalidationdata. Gräwe et al., in prep.

  15. Seasonalityoftidalforcing Howdoesthisaffect sedimenttransport due totidalasymmetries (M4)? Gräwe et al. (in prep.) Müller et al. (in prep.)

  16. Stratification in the North SeaBesides tides, seasonal stratification is characteristic for the North Sea dynamics. Annual cycleoftemprature stratification in the Northern North Sea (asseenfrom a 1D model) Boldingand Burchard (2002)

  17. Stratificationisspatially not homogeneous Tidal front Doggerbank Doggerbank Model resultsby Burchard & Bolding, 2002

  18. Tidalfronts Tidalfronts(stratified in deep, mixed in shallowwater) are an environmentallyveryimportantphenomenon. Thus, in shallowwaterthebottomsedimentis in directcontactwiththesurfacewaters, whereas in deeperwaters, thebottomlayersareclearlyseparatedfromthesurfacewates.

  19. Whatdeterminesthepositionoftidalfronts ? Stabilising: waterdepthH, surfacebuoyancyfluxQ (heatflux, netprecipitation). Destabilising: tidesgivenastidalvelocityamplitudeu. Importantparameterby dimensional analysis: (Q * H) / u3 Large:stablystratified; Small:mixed Note: H / u3isthefamous Simpson-Hunter (1974) parameter.

  20. Tidal mixing fronts in the Irish Sea stratified & deep mixed & shallow mixed & very shallow & warm or stratified due to river run-off Satellite images courtesy Alejandro Souza

  21. Tidal Mixing fronts in the Irish Sea Stratification Simpson-Hunter parameter Numerical model result, Souza et al., in press.

  22. Environmental effectsofseasonalthermal stratification Surfaceheatflux (cumulated) during FLEX‘76 Burchard, 2002

  23. FLEX 1976 Lateral effects aresmall, such that one-dimensional modellingmaybe successful Burchard, 2002

  24. Summer stratificationalong 56°North Seatransect

  25. Summer chlorophyllconc. along 56°North Seatransect

  26. Northern North Sea: Annual cycleof stratificationand primaryproduction Burchard et al., 2005 Burchard, 2002

  27. Rotatingbulkshear in Monterey Bay Itsweire et al. (1989)

  28. PROVESS-NNS study site (observations: Sep-Nov 1998) Wind ADCP, CTD, MST

  29. Bulk property observations in NNS Wind Bulk shear squared Bulk shear direction vs. inertial rotation

  30. Theory I 1D dynamic equations: Layer averaging:

  31. Dynamic equationforbulkshearsquared: Conclusion: Assumingbed stress beingsmall, bulkshearisgenerated bythealignmentof wind vectorandshearvector.

  32. Application of theory to observations

  33. Impact of bulk shear on diapycnal mixing Conclusion: Increased interfacial mixing rates correlate with high shear. Can we resolve this in 3D models?

  34. Transect in NNS Observations (Scanfish data from BSH) Model results (GETM with adaptive coordinates) Gräwe et al. (in prep.)

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