Advertisement

Ocean Dynamics

, Volume 63, Issue 8, pp 865–880 | Cite as

Simulations of a Line W-based observing system for the Atlantic meridional overturning circulation

  • Matthias FischerEmail author
  • Arne Biastoch
  • Erik Behrens
  • Johanna Baehr
Article

Abstract

In a series of observing system simulations, we test whether the Atlantic meridional overturning circulation (AMOC) can be observed based on the existing Line W deep western boundary array. We simulate a Line W array, which is extended to the surface and to the east to cover the basin to the Bermuda Rise. In the analyzed ocean circulation model ORCA025, such an extended Line W array captures the main characteristics of the western boundary current. Potential trans-basin observing systems for the AMOC are tested by combining the extended Line W array with a mid-ocean transport estimate obtained from thermal wind “measurements” and Ekman transport to the total AMOC (similarly to Hirschi et al., Geophys Res Lett 30(7):1413, 2003). First, we close Line W zonally supplementing the western boundary array with several “moorings” in the basin (Line W-32°N). Second, we supplement the western boundary array with a combination of observations at Bermuda and the eastern part of the RAPID array at 26°N (Line W-B-RAPID). Both, a small number of density profiles across the basin and also only sampling the eastern and western boundary, capture the variability of the AMOC at Line W-32°N and Line W-B-RAPID. In the analyzed model, the AMOC variability at both Line W-32°N and Line W-B-RAPID is dominated by the western boundary current variability. Away from the western boundary, the mid-ocean transport (east of Bermuda) shows no significant relation between the two Line W-based sections and 26°N. Hence, a Line W-based AMOC estimate could yield an estimate of the meridional transport that is independent of the 26°N RAPID estimate. The model-based observing system simulations presented here provide support for the use of Line W as a cornerstone for a trans-basin AMOC observing system.

Keywords

Atlantic meridional overturning circulation Observing system simulations Line W RAPID 

Notes

Acknowledgments

We thank John Toole for providing information about Line W and valuable scientific discussions. We thank both reviewers for their constructive and valuable comments which helped to significantly improve the manuscript. This work was supported by the Cooperative Project “RACE - Regional Atlantic Circulation and Global Change” funded by the German Federal Ministry for Education and Research (BMBF), 03F0651A, and by the CliSAP Cluster of Excellence at the University of Hamburg funded through the Deutsche Forschungsgemeinschaft (M.F. and J.B.). The research leading to the presented results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no 212643 (EU-THOR) (A.B., E.B). The model integration was performed at the North-German Supercomputing Alliance (HLRN). Data from the RAPID-WATCH MOC monitoring project are funded by the Natural Environment Research Council and are freely available from http://www.noc.soton.ac.uk/rapidmoc.

References

  1. Baehr J, Hirschi J, Beismann J, Marotzke J (2004) Monitoring the meridional overturning circulation in the North Atlantic: a model-based array design study. J Mar Res 62(3):283–312CrossRefGoogle Scholar
  2. Barnier B, Madec G, Penduff T, Molines JM, Treguier AM, Beckmann A, Biastoch A, Böning C, Dengg J, Derval C, Durand E, Gulev S, Le Sommer J, Remy E, Talandier C, Theetten S, Maltrud M (2006) Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy permitting resolution. Ocean Dyn 56:543–567. doi: 10.1007/s10236-006-0082-1 CrossRefGoogle Scholar
  3. Biastoch A, Böning CW, Getzlaff J, Molines JM, Madec G (2008) Causes of inter-annual-decadal variability in the meridional overturning circulation of the midlatitude North Atlantic Ocean. J Clim 21:6599–6615. doi: 10.1175/2008JCLI2404.1 CrossRefGoogle Scholar
  4. Bingham RJ, Hughes CW (2008) Determining North Atlantic meridional transport variability from pressure on the western boundary: a model investigation. J Geophys Res 113:C09008. doi: 10.1029/2007JC004679 CrossRefGoogle Scholar
  5. Bingham RJ, Hughes CW, Roussenov V, Williams RG (2008) Meridional coherence of the North Atlantic meridional overturning circulation. Geophys Res Lett 34:L23606. doi: 10.1029/2007GL031731 Google Scholar
  6. Chidichimo M, Kanzow T, Cunningham S, Johns W, Marotzke J (2010) The contribution of eastern-boundary density variations to the Atlantic meridional overturning circulation at 26.5°N. Ocean Sci 6:475–490CrossRefGoogle Scholar
  7. Cunningham S, Kanzow T, Rayner D, Baringer M, Johns W, Marotzke J, Longworth H, Grant E, Hirschi J, Beal L et al. (2007) Temporal variability of the Atlantic meridional overturning circulation at 26.5°N. Science 317:935–938CrossRefGoogle Scholar
  8. Cunningham S et al. (2010) The present and future system for measuring the Atlantic meridional overturning circulation and heat transport. In: Hall J, Harrison D E, Stammer D (eds) Proceedings of OceanObs’09: sustained ocean observations and information for society, September 2009, vol 2. ESA Publication WPP-306, Venice, pp. 21-25. doi: 10.5270/OceanObs09.cwp.21
  9. The DRAKKAR Group, Barnier B, Brodeau L, Le Sommer J, Molines JM, Penduff T, Theetten S, Treguier AM, Madec G, Biastoch A, Böning C, Dengg J, Gulev S, Bourdallé Badie R, Chanut J, Garric G, Alderson S, Coward A, de Cuevas B, New A, Haines K, Smith G, Drijfhout S, Hazeleger W, Severijns C, Myers P (2006) Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy permitting resolution. Ocean Dyn 56:543–567. doi: 10.1007/s10236-006-0082-1 CrossRefGoogle Scholar
  10. Goosse H, Fichefet T (1999) Importance of ice-ocean interactions for the global ocean circulation: a model study. J Phys Oceanogr 104(C10):23,337–23,355. doi: 10.1029/1999JC900215 Google Scholar
  11. Hirschi J, Baehr J, Marotzke J, Stark J, Cunningham S, Beismann J (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophys Res Lett 30(7):1413. doi: 10.1029/2002GL016776 CrossRefGoogle Scholar
  12. Jackett DR, McDougall TJ (1995) Minimal adjustment of hydrographic data to achieve static stability. J Atmos Ocean Technol 12:381–389CrossRefGoogle Scholar
  13. Kanzow T, Cunningham S, Rayner D, Hirschi J, Johns W, Baringer M, Bryden H, Beal L, Meinen C, Marotzke J (2007) Observed flow compensation associated with the MOC at 26.5°N in the Atlantic. Science 317(5840):938–941. doi: 10.1126/science.1141293 CrossRefGoogle Scholar
  14. Kanzow T, Johnson HL, Marshall DP, Cunningham S, Hirschi J, Mujahid A, Bryden H, Johns W (2009) Basinwide integrated volume transports in an eddy-filled ocean. J Phys Oceanogr 39:3091–3110. doi: 10.1175/2009JPO4185.1 CrossRefGoogle Scholar
  15. Kanzow T, Cunningham S, Johns W, Hirschi J, Marotzke J, Baringer M, Meinen C, Chidichimo M, Atkinson C, Beal L, Bryden H, Collins J (2010) Seasonal variability of the Atlantic meridional overturning circulation at 26.5°N. J Clim 23(21):5698–5678. doi: 10.1175/2010JCLI3389.1 CrossRefGoogle Scholar
  16. Large WG, Yeager S (2009) The global climatology of an inter-annually varying air-sea flux data set. Clim Dyn 33:342–364CrossRefGoogle Scholar
  17. Lee T, Marotzke J (1998) Seasonal cycles of meridional overturning and heat transport of the Indian Ocean. J Phys Oceanogr 28:923–943. doi: 10.1175/1520-0485(1998)028<<0923:SCOMOA>>2.0.CO;2 CrossRefGoogle Scholar
  18. Madec G (2008) NEMO reference manual, ocean dynamics component : NEMO-OPA. Preliminary Version, Tech. Rep. 27, Note du Pôle de modélisation, Institut Pierre-Simon Laplace (IPSL). France, ISSN No 1288–1619, 2008Google Scholar
  19. Marotzke J, Giering R, Zhang K, Stammer D, Hill C, Lee T (1999) Construction of the adjoint MIT ocean general circulation model and application to Atlantic heat transport sensitivity. J Geophys Res 104:29,529–29,547. doi: 10.1029/1999JC900236 CrossRefGoogle Scholar
  20. Phillips H, Joyce T (2007) Bermuda’s tale of two time series: Hydrostation S and BATS. J Phys Oceanogr 37:554–571. doi: 10.1175/JPO2997.1 CrossRefGoogle Scholar
  21. Toole JM, Curry R, Joyce T, McCartney M, Peña-Molino BP (2011) Transport of the North Atlantic Deep Western Boundary Current about 39°N, 70°W: 2004-2008. Deep-Sea Res II 58(2011):1768–1780. doi: 10.1016/j.dsr2.2010.10.058 CrossRefGoogle Scholar
  22. Willis J (2010) Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning. Geophys Res Lett 37:L06602. doi: 10.1029/2010GL042372 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Matthias Fischer
    • 1
    Email author
  • Arne Biastoch
    • 2
  • Erik Behrens
    • 2
  • Johanna Baehr
    • 1
  1. 1.Institute of Oceanography, KlimaCampusUniversity of HamburgHamburgGermany
  2. 2.GEOMAR Helmholtz-Zentrum für Ozeanforschung KielKielGermany

Personalised recommendations