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Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde

Numerical model applications to lakes and estuaries with focus on transport and mixing of tracers. . Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde hans.burchard@io-warnemuende.de. Programme Thermohaline circulation & sediment transport in the Wadden Sea

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Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde

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  1. Numerical model applications to lakes and estuaries with focus on transport and mixing of tracers. Hans Burchard Leibniz Institute for Baltic Sea Research Warnemünde hans.burchard@io-warnemuende.de

  2. Programme Thermohalinecirculation & sedimenttransport in theWaddenSea Basin-widemixing in lakes due toseiches

  3. WaddenSea … and … thermo-halinecirculation? www.rapid.ac.uk

  4. WarmingPrecipitation Land Ocean Downwardsurfacebuoyancyflux Seabed Weaktidalmixing: verticallystratified River Estuarinecirculation Strong tidalmixing: horizontallystratified

  5. Global ocean: Spatiallyinhomogeneoussurfacebuoyancyfluxesplus internalmixingleadsto global overturningcirculation. WaddenSea: Spatiallyhomogenoussurfacebuoyancyfluxesoverslopingbathymetry plus tidalmixingshouldleadtoredidualoverturningcirculation. But doesitreally happen?

  6. Howcanweapproachthis withobservations ? Locations of five automatic monitoring poles in the Wadden Sea of the German Bight, recording temperature and salinity, (and thus density). Burchard et al. (JPO 2008)

  7. Climatology: Salinitydifference HW-NW Burchard et al. (JPO 2008)

  8. Climatology: Temperaturedifference HW-LW Burchard et al. (JPO 2008)

  9. Climatology: Densitydifference HW-LW Burchard et al. (JPO 2008)

  10. Implicationsfor sedimenttransport Suspended matter concentrations are substantially increased in the Wadden Sea of the German Bight, without having significant sources at the coast. Why ? Total suspended matter from MERIS/ENVISAT on August, 12, 2003.

  11. Model approach: 1. Simulating a closed Wadden Sea basin (Sylt-Rømø bight) with small freshwater-runoff and net precipitation. 2. Spin up model with variable and with constant density until periodic steady state. 3. Then initialise both scenarios with const. SPM concentration. 4. Quantify SPM content for control volume. Burchard et al. (JPO 2008)

  12. Computer simulations in Sylt-Rømø Bight Wassertiefe Burchard et al. (JPO 2008)

  13. Surface salinity at high and low water Burchard et al. (JPO 2008)

  14. Withdensitydifferences Total waterand SPM volume V / km3 Burchard et al. (JPO 2008)

  15. Withoutdensitydifferences Total waterand SPM volume V / km3 Burchard et al. (JPO 2008)

  16. Sealevelrise & tidal flat growth (DanishWaddenSea) Data andgraphicsfrom Morten Pejrup, Copenhagen University

  17. WaddenSea model Model systembased on GETM: NA: 5.4 km X 5.4 km (2D) NSBS: 1.8 km X 1.8 km (3D) SNS, WBS: 600 m X 600 m (3D) WaddenSea: 200 m X 200 m (3D) PACE project (NWO-BMBF): „The futureoftheWaddenSea sedimentfluxes: Still keepingpace withsealevelrise?“ (2011-2014) Gräwe et al., in prep.

  18. Model validation (600 m resolution) Sealevel Temperature Salinity Sa Gräwe et al., in prep.

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

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

  21. Seasurfacesalinity in theWaddenSea (asseen in 200 m resolution model) Personal communication Matias Duran Matute (NIOZ)

  22. Simulation Lake Alpnach(Switzerland) Becherer & Umlauf (2011)

  23. Simulation Lake Alpnach(Switzerland) Becherer & Umlauf (2011)

  24. Simulation Lake Alpnach(Switzerland) Becherer & Umlauf (2011)

  25. Simulation Lake Alpnach(Switzerland) Becherer & Umlauf (2011)

  26. Basin-Scale Mixing deep-water average of mixing (depth > 15 m) Becherer & Umlauf (2011)

  27. Baltic Sea Tracer Experiment (BATRE) • Goal: quantify deep-water mixing in the central Baltic Sea • Pilot study for new inert tracer gas (CF3SF5, now standard) • 5 tracer surveys within 2 years • Mooring arrays and turbulence measurements • High-resolution nested 3-D model (GETM) • 600 m lateral resolution • 200 sigma-type layers (vertically adaptive, Hofmeister et al. 2010) • Second-moment turbulence closure model (GOTM, www.gotm.net)

  28. Principleofbasin-widemixing Reissmann et al. 2009 Mixing processes in the Baltic Sea Courtesy Peter Holtermann

  29. Principleofbasin-widemixing Reissmann et al. 2009 Investigation ofdeepwatermixingduring a stagnationperiod Courtesy Peter Holtermann

  30. Boundary Mixing Internal Mixing Reissmann et al. 2009 Investigation ofdeepwatermixingduring a stagnationperiod Courtesy Peter Holtermann

  31. Vertical Mixing Rates Initial stage (before boundary contact):   10-6 m2 s-1 Late stage (after boundary contact):  ~ 10-5 m2 s-1 Interior mixing Intrusions Boundary mixing

  32. Numerical Model Results data model February 2009 August 2008 October 2007 January 2008 Holtermann et al. (submitted) model feels boundary mixing to early

  33. Take home: Differential buoyancylosses (overslopingtopography) driveoverturningcirculation in coastalseasandlakes. This causesnetsedimentfluxesintothe Waden Seawhich mayexplainwhytheWaddenSeasurvivedpastandmaysurvive futuresealevelrise. Seiches in lakesandotherstratifiedbasinscauseboundarymixing typicallyincreaseseffectivemixingbyaboutoneorderofmagnitude. Question: Can wemake a 3D modelfor a deeplake such thatwe canproperlypredicttheeffectivebasin-widemixing? Forthe Baltic Seathisworked (Holtermann et al., in revision), but lakes arenarrowerandoftenevendeeper.

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