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2nd NACLIM Annual Meeting, Trieste , 1.- 2. Oktober 2013

Stirring and mixing in the Denmark Strait Overflow Detlef Quadfasel (Hamburg) with contributions by Kerstin Jochumsen , Nuno Nunes (Hamburg) Janin Schaffer, Torsten Kanzow , Jürgen Fischer (Kiel). 2nd NACLIM Annual Meeting, Trieste , 1.- 2. Oktober 2013.

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2nd NACLIM Annual Meeting, Trieste , 1.- 2. Oktober 2013

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  1. Stirring and mixing in the Denmark Strait Overflow DetlefQuadfasel (Hamburg) with contributions by Kerstin Jochumsen, NunoNunes (Hamburg) Janin Schaffer, TorstenKanzow, Jürgen Fischer (Kiel) 2nd NACLIM Annual Meeting, Trieste, 1.- 2. Oktober 2013

  2. Temperaturestructureoverflow DenmarkStraitϴ ~ - 0.5°C, S ~ 34.95 100 km GreenlandIceland

  3. Downstream temperatures DenmarkStraitϴ ~ - 0.5°C, S ~ 34.85 100 km GreenlandIceland 1000 km downstreamϴ ~+1.5°C, S ~ 34.95 2000 km GreenlandIreland

  4. Strong entrainment Less intense but continuing entrainment Entrainmentalongthepath Voet & Quadfasel, 2010

  5. Stirringthrougheddies Voet & Quadfasel, 2010 Obs. Model Fischer et al., subm.

  6. Stirringandmixing 1 2 3

  7. Stirringandmixing 1 Verticalmixing KH-Inst 2 3 V. van Gogh, 1889

  8. Stirringandmixing 1 Verticalmixing KH-Inst 2 3 V. van Gogh, 1889 Eddy-stirring J. Girton, 2001

  9. Mixing experiment June-August 2012 MERIAN MSM 21 POSEIDON PO 451 1 2 3 CTD/lADCP/MicroStructure Moorings AUV CTD & MSS

  10. Moorings N E C W S E N Mooring array (12 m.) 2 months in water coverage 20 x 25 km coherentfor t > 1 day W S

  11. Problems ADCP (1) ADCP Four ADCPs in centralarray RCM (colour) and ADCP (black) recordsat 20 m a.b.

  12. Problems ADCP (2) ADCP data shows velocity bias near bottom Bias affects also older data, albeit to lesser extent Undergoing discussion with manufacturer to understand and mitigate problem

  13. Problems ADCP (3) Can wetrustthelongtermtransport time seriesofoverflows? Weareworking on theanswer.

  14. Results: Hydrography Verticaldistributionatcentralmooring High coherencealongandacrossslope. Signal propagation ~ 0.6 m/s

  15. Temperaturevariations on pressurelevels

  16. Zoom in

  17. Microstructureprofiling Dissipation rate at top edge of DS overflow plume three orders of magnitude greater than background value (e: 10-9 → 10-6 W / Kg) Comparable values measured by AUV crossing horizontal edges of plume(for further details, see Paka et al, 2013, Ocean Sci. Discuss.)

  18. AUV tracksduring MSM21 AUV equippedwith ADCP, CTD andMicrostructureprobes. Schaffer & Kanzow

  19. Hydrographyanddissipation Schaffer & Kanzow

  20. Internal wavesanddissipation Schaffer & Kanzow

  21. Final remarks There‘smoreworktobedonetoestimatethemixing in theplume The ADCP biasneedstobefurtherexplored

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