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WAVE array update and modelling background

WAVE array update and modelling background. Chris W. Hughes, Miguel Angel Morales Maqueda, Shane Elipot, Rory Bingham 1 NOC (Proudman Building, Liverpool) 1 ex POL, now University of Newcastle. Bingham et al., GRL 2007. A good rule of thumb:

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WAVE array update and modelling background

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  1. WAVE array update and modelling background Chris W. Hughes, Miguel Angel Morales Maqueda, Shane Elipot, Rory Bingham1 NOC (Proudman Building, Liverpool) 1 ex POL, now University of Newcastle

  2. Bingham et al., GRL 2007

  3. A good rule of thumb: Assume a layer thickness of 1000 m, and a midlatitude f = 10-4 Then 1 cm of sea level or 1 mbar of pressure represents 1 Sv of transport

  4. Northward transports, integrated zonally and over the depth ranges 100-1300 m 1300-3000 m Actual transports, and transports from pressure differences Using pressures from east and west Using pressures from west only, and ignoring any pressure changes which are constant with depth. Bingham and Hughes, JGR 2008

  5. Sv -4 -3 -2 -1 0 1 2 3 4 Bingham and Hughes, GRL 2009

  6. Assuming 16 cm standard deviation

  7. Hughes and Williams, JGR 2010

  8. 1/12 degree OCCAM bottom pressure variability (17 years of 5-day means)

  9. 1/12 degree OCCAM bottom pressure residual variability (17 years of 5-day means)

  10. Total Difference from eastern boundary mean 0.75 2.5 0.20 2.0 cm

  11. 1/12 degree model: First EOF of bottom pressure , 1985-2001 -1 0 1

  12. Sv -4 -3 -2 -1 0 1 2 3 4 Bingham and Hughes, GRL 2009

  13. ¼ degree model: 6-year mean bottom pressure anomaly, 1992-1997

  14. First EOF of bottom pressure in a 50-year MICOM simulation at ¼ degree (simulation by Vassil Roussenov)

  15. Zhang, GRL 2010 GFDL CM2.1 (coarse resolution coupled climate model) Meridional coherence of MOC when plotted in density coordinates

  16. Southward transport of NADW Marsh et al., GRL 2005 ¼ degree OCCAM

  17. Line B (2004-2008) RS Line (2008-…)

  18. RS1 RS2 RS3 RS4 RS5 RS6

  19. Pressure difference between RS1 and RS2 Direct measurement Reconstruction from currents and density A pressure of 10 Pa is equivalent to 1 mm of water

  20. Pressure difference between RS2 and RS4 Direct measurement Reconstruction from currents and density A pressure of 10 Pa is equivalent to 1 mm of water

  21. Directly-measured pressure differences relative to 1100 m (RS1), and differences inferred using the stepping method ( 1-50 day band pass filter)

  22. Conclusions • We have an in-situ monitoring system for pressure differences that can produce drift-free measurements with 0.2-0.3 mbar accuracy. • Models suggest that subcentimetre variability in the western basin is limited to a narrow strip on the continental slope. • A variety of models show interannual bottom pressure variations being dominated by an MOC-like mode in this strip. • This mode seems to continue throughout the western half of the Labrador Sea

  23. Simple, works fairly well, ignores complex topography Assumes topographic steering dominates. Works better, but ignores one component of velocity. Assumes topographic steering dominates but generalises to include both velocity components. Works better still, and reduces to simple case when topography is smooth.

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