Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Directly measured mid-depth circulation in the northeastern North Atlantic Ocean


The circulation of water masses in the northeastern North Atlantic Ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes1. But the ocean circulation at depths below the reach of satellite observations is difficult to measure, and only recently have comprehensive, direct observations of whole ocean basins been possible2,3,4. Here we present quantitative maps of the absolute velocities at two levels in the northeastern North Atlantic as obtained from acoustically tracked floats. We find that most of the mean flow transported northward by the Gulf Stream system at the thermocline level (about 600 m depth) remains within the subpolar region, and only relatively little enters the Rockall trough or the Nordic seas. Contrary to previous work5,6, our data indicate that warm, saline water from the Mediterranean Sea reaches the high latitudes through a combination of narrow slope currents and mixing processes. At both depths under investigation, currents cross the Mid-Atlantic Ridge preferentially over deep gaps in the ridge, demonstrating that sea-floor topography can constrain even upper-ocean circulation patterns.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Float trajectories.
Figure 2: Mean potential temperature (colour shading) on two density surfaces in the subpolar North Atlantic corresponding to the two levels of the float data.
Figure 3: Mean streamfunction for the subpolar North Atlantic from subsurface float data at two levels.
Figure 4: Floats crossing the Mid-Atlantic Ridge.


  1. Siedler, G., Church, J. & Gould, J. (eds) Ocean Circulation and Climate—Observing and Modelling the Global Ocean International Geophysics Series 77 (Academic, San Diego, 2001)

  2. Davis, R. E. & Zenk, W. in Ocean Circulation and Climate—Observing and Modelling the Global Ocean International Geophysics Series 77 (eds Siedler, G., Church, J. & Gould, J.) 123–139 (Academic, San Diego, 2001)

    Book  Google Scholar 

  3. Lavender, K. L., Davis, R. E. & Owens, W. B. Direct velocity measurements describe a new circulation regime in the Labrador and Irminger Seas. Nature 407, 66–69 (2000)

    Article  ADS  CAS  Google Scholar 

  4. Davis, R. Preliminary results from directly measuring mid-depth circulation in the tropical and South Pacific. J. Geophys. Res. 103, 24619–24639 (1998)

    Article  ADS  Google Scholar 

  5. Reid, J. L. On the mid-depth circulation and salinity field in the North Atlantic Ocean. J. Geophys. Res. 83, 5063–5067 (1978)

    Article  ADS  Google Scholar 

  6. Reid, J. L. On the contribution of Mediterranean Sea outflow to the Norwegian-Greenland Sea. Deep-Sea Res. 26, 1199–1223 (1979)

    Article  ADS  Google Scholar 

  7. Bower, A. S. et al. Warm-water pathways in the Subpolar North Atlantic: An overview of the ACCE RAFOS float programme. WOCE Int. Newsl. 38, 14–16 (2000)

    Google Scholar 

  8. Speer, K., Gould, J. & LaCasce, J. Year-long float trajectories in the Labrador Sea Water of the eastern North Atlantic Ocean. Deep-Sea Res. II 46, 165–179 (1999)

    Article  ADS  Google Scholar 

  9. Le Cann, B., Speer, K. A., Serpette, A., Paillet, J. & Reynaud, T. Lagrangian observations in the intergyre North-East Atlantic during the ARCANE and EUROFLOAT projects: Early results. WOCE Int. Newsl. 34, 25–27 (1999)

    Google Scholar 

  10. Curry, R. G. A Database of Hydrographic Stations and Tools for Climatological Analysis Technical Report WHOI-96-01 (Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, 1996)

    Book  Google Scholar 

  11. McCartney, M. S. & Mauritzen, C. On the origin of the warm inflow to the Nordic Seas. Prog. Oceanogr. 51, 125–214 (2001)

    Article  ADS  Google Scholar 

  12. McCartney, M. S. & Talley, L. D. Warm-to-cold conversion in the northern North Atlantic Ocean. J. Phys. Oceanogr. 14, 922–935 (1984)

    Article  ADS  Google Scholar 

  13. Paillet, J., Arhan, M. & McCartney, M. S. Spreading of Labrador Sea water in the eastern North Atlantic. J. Geophys. Res. 103, 10223–10239 (1998)

    Article  ADS  CAS  Google Scholar 

  14. Talley, L. D. & McCartney, M. S. Distribution and circulation of Labrador Sea water. J. Phys. Oceanogr. 12, 1189–1205 (1982)

    Article  ADS  Google Scholar 

  15. Dickson, R. R. & Brown, J. The production of North Atlantic deep water: Sources, rates, and pathways. J. Geophys. Res. 99, 12319–12341 (1994)

    Article  ADS  Google Scholar 

  16. Worthington, L. V. On the North Atlantic circulation. Johns Hopkins Oceanogr. Stud. 6, 1–110 (1976)

    Google Scholar 

  17. Pollard, R., Read, J. & Holliday, P. Circulation and mode waters of the North Atlantic subpolar gyre in 1996. WOCE Int. Newsl. 37, 21–27 (1999)

    Google Scholar 

  18. Krauss, W. The North Atlantic Current. J. Geophys. Res. 91, 5061–5074 (1986)

    Article  ADS  Google Scholar 

  19. Rossby, T. The North Atlantic current and surrounding waters: At the crossroads. Rev. Geophys. 34, 463–481 (1996)

    Article  ADS  Google Scholar 

  20. Belkin, I. M. & Levitus, S. Temporal variability of the Subarctic Front near the Charlie-Gibbs Fracture Zone. J. Geophys. Res. 101, 28317–28324 (1996)

    Article  ADS  Google Scholar 

  21. Sy, A., Schauer, U. & Meincke, J. The North Atlantic Current and its associated hydrographic structure above and eastwards of the Mid-Atlantic Ridge. Deep-Sea Res. 39, 825–853 (1992)

    Article  ADS  Google Scholar 

  22. Heywood, K. J., McDonagh, E. L. & White, M. A. Eddy kinetic energy of the North Atlantic subpolar gyre from satellite altimetry. J. Geophys Res. 99, 22525–22539 (1994)

    Article  ADS  Google Scholar 

  23. Iorga, M. C. & Lozier, M. S. Signatures of the Mediterranean outflow from a North Atlantic climatology, diagnostic velocity fields. J. Geophys. Res. 104, 26011–26029 (1999)

    Article  ADS  Google Scholar 

  24. Pingree, R. D. & LeCann, B. Structure, strength and seasonality of the slope currents in the Bay of Biscay region. J. Mar. Biol. Assoc. UK 70, 857–885 (1990)

    Article  Google Scholar 

  25. Bersch, M., Meincke, J. & Sy, A. Interannual thermocline changes in the northern North Atlantic. Deep Sea Res. II 46, 55–75 (1999)

    Article  ADS  Google Scholar 

  26. Bersch, M. NAO-induced changes of the upper-layer circulation in the northern North Atlantic Ocean. J. Geophys. Res. (in the press)

  27. Schmitz, W. J. Jr & McCartney, M. S. On the North Atlantic circulation. Rev. Geophys. 31, 29–49 (1993)

    Article  ADS  Google Scholar 

  28. Rossby, H. T., Levine, E. & Conners, D. N. The isopycnal Swallow Float: A simple device for tracking water parcels in the ocean. Prog. Oceanogr. 14, 511–525 (1985)

    Article  ADS  Google Scholar 

  29. Freeland, H. J. & Gould, W. J. Objective analysis of meso-scale ocean circulation features. Deep-Sea Res. 23, 915–923 (1976)

    Google Scholar 

  30. Zhang, H. M., Prater, M. D. & Rossby, T. Isopycnal Lagrangian statistics from the North Atlantic current RAFOS float observations. J. Geophys. Res. 106, 13817–13836 (2001)

    Article  ADS  Google Scholar 

Download references


We thank all the technicians and research assistants who contributed to this project for their help and support. We also thank H. Hunt Furey for help in the preparation of the figures. This work was supported by the US National Science Foundation, the Deutsche Forschungsgemeinschaft, the Institut Français de Recherche pour l'Exploitation de la Mer, the Centre National de la Recherche Scientifique, and the European Commission EUROFLOAT project.

Author information

Authors and Affiliations


Corresponding author

Correspondence to A. S. Bower.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bower, A., Le Cann, B., Rossby, T. et al. Directly measured mid-depth circulation in the northeastern North Atlantic Ocean. Nature 419, 603–607 (2002).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing