Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

Observed sources and variability of Nordic seas overflow

Nature Geoscience volume 2, pages 406–410 (2009)Cite this article

Abstract

The overflows from the Nordic seas maintain the deep branch of the North Atlantic Ocean’s thermohaline circulation1,2, an important part of the global climate system3,4. However, the source of these overflows, and of overflow variability, is debated: proposals include open-ocean convection, dense-water production on the Arctic shelves and the gradual transformation of Atlantic water as it circulates the periphery of the Nordic seas and the Arctic Ocean2,5,6. Here we analyse time series of observed ocean temperature and salinity between 1950 and 2005. We find that the progression of thermohaline anomalies on interannual to decadal timescales does not support a systematic response of the overflow properties to convective mixing in the Greenland Sea as has been suggested7,8. Instead, anomalies in temperature and salinity that leave the northern seas at the Denmark Strait have travelled along the rim of the Nordic seas from inflow to overflow. Furthermore, the Faroe–Shetland Channel reflects the variability of an overturning loop within the Norwegian Sea that has not been observed previously. We thus conclude that the Atlantic water circulating in the Nordic seas is the main source for change in the overflow waters.

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

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Climatological temperature of the Nordic seas at 200 m depth.
Figure 2: The observational time series.
Figure 4: Thermohaline properties of sources and overflows, and the associated overflow compositions.
Figure 3: Normalized time series of overflow hydrography and Atlantic-derived sources of variability.

Similar content being viewed by others

References

  1. Dickson, R. R. & Brown, J. The production of North Atlantic deep water: Sources, rates and pathways. J. Geophys. Res. 99, 12319–12342 (1994).

    Article  Google Scholar 

  2. Hansen, B. & Østerhus, S. North Atlantic–Nordic Seas exchanges. Prog. Oceanogr. 45, 109–208 (2000).

    Article  Google Scholar 

  3. Rahmstorf, S. Ocean circulation and climate during the past 120,000 years. Nature 419, 207–214 (2002).

    Article  Google Scholar 

  4. Kleiven, H. F. et al. Reduced North Atlantic deep water coeval with the glacial Lake Agassiz fresh water outburst. Science 319, 60–64 (2008).

    Article  Google Scholar 

  5. Mauritzen, C. Production of dense overflow waters feeding the North Atlantic across the Greenland–Scotland Ridge. Part 1: Evidence for a revised circulation scheme. Deep-Sea Res. I 43, 769–806 (1996).

    Article  Google Scholar 

  6. Rudels, B., Friedrich, H. J. & Quadfasel, D. The arctic circumpolar boundary current. Deep-Sea Res. II 46, 1023–1062 (1999).

    Article  Google Scholar 

  7. Schlosser, P., Bönisch, G., Rhein, M. & Bayer, R. Reduction of deepwater formation in the Greenland Sea during the 1980s: Evidence from tracer data. Science 251, 1054–1056 (1991).

    Article  Google Scholar 

  8. Dong, B. & Sutton, R. W. Mechanism of interdecadal thermohaline circulation variability in a coupled ocean–atmosphere GCM. J. Clim. 18, 1117–1135 (2005).

    Article  Google Scholar 

  9. Dickson, B., Meincke, J., Vassie, I., Jungclaus, J. & Østerhus, S. Possible predictability in overflow from the Denmark Strait. Nature 397, 243–246 (1999).

    Article  Google Scholar 

  10. Nilsen, J. E. Ø., Hátún, H., Mork, K. A. & Valdimarsson, H. The NISE Data Set. Technical Report 08-01 (Faroese Fisheries Laboratory, Box 3051, Tórshavn, Faroe Islands, 2008).

  11. Hansen, B. & Østerhus, S. Faroe Bank Channel overflow 1995–2005. Prog. Oceanogr. 75, 817–856 (2007).

    Article  Google Scholar 

  12. Skagseth, Ø. et al. in Arctic–Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate (eds Dickson, B., Meincke, J. & Rhines, P.) 45–64 (Springer, 2008).

    Book  Google Scholar 

  13. Blindheim, J. & Østerhus, S. in The Nordic Seas: An Integrated Perspective (eds Drange, H., Dokken, T. M., Furevik, T., Gerdes, R. & Berger, W.) 11–38 (Geophysical Monograph Series 158, American Geophysical Union, 2005).

    Google Scholar 

  14. Jonsson, S. & Valdimarsson, H. A new path for the Denmark Strait overflow water from the Iceland Sea to Denmark Strait. Geophys. Res. Lett. 31, L03305 (2004).

    Article  Google Scholar 

  15. Olsson, K. A. et al. Intermediate water from the Greenland Sea in the Faroe Bank Channel: Spreading of released sulphur hexafluoride. Deep-Sea Res. I 52, 279–294 (2005).

    Article  Google Scholar 

  16. Poulain, P.-M., Warn-Varnas, A. & Niiler, P. P. Near-surface circulation of the Nordic seas as measured by Lagrangian drifters. J. Geophys. Res. 101, 18237–18258 (1996).

    Article  Google Scholar 

  17. Read, J. F. & Pollard, R. T. Water masses in the region of the Iceland-Færoes front. J. Phys. Oceanogr. 22, 1365–1378 (1992).

    Article  Google Scholar 

  18. Søiland, H., Prater, M. D. & Rossby, T. Rigid topographic control of currents in the Nordic Seas. Geophys. Res. Lett. 35, L18607 (2008).

    Article  Google Scholar 

  19. Curry, R. & Mauritzen, C. Dilution of the northern North Atlantic Ocean in recent decades. Science 308, 1772–1774 (2005).

    Article  Google Scholar 

  20. Holliday, N. P. et al. Reversal of the 1960s to 1990s freshening trend in the northeast North Atlantic and Nordic Seas. Geophys. Res. Lett. 35, L03614 (2008).

    Article  Google Scholar 

  21. Dickson, R. R., Meincke, J., Malmberg, S.-A. & Lee, A. J. The great salinity anomaly in the Northern North Atlantic 1968–1982. Prog. Oceanogr. 20, 103–151 (1988).

    Article  Google Scholar 

  22. Dickson, B. et al. in Arctic–Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate (eds Dickson, B., Meincke, J. & Rhines, P.) 443–474 (Springer, 2008).

    Book  Google Scholar 

  23. Olsson, K. A., Jeansson, E., Tanhua, T. & Gascard, J.-C. The East Greenland current studied with CFCs and released sulphur hexafluoride. J. Mar. Syst. 55, 77–95 (2005).

    Article  Google Scholar 

  24. Furevik, T. On anomalous sea surface temperatures in the Nordic Seas. J. Clim. 13, 1044–1053 (2000).

    Article  Google Scholar 

  25. Turrell, W. R., Slesser, G., Adams, R. D., Payne, R. & Gillibrand, P. A. Decadal variability in the composition of Faroe–Shetland Channel bottom water. Deep-Sea Res. I 46, 1–25 (1999).

    Article  Google Scholar 

  26. Eldevik, T., Straneo, F., Sandø, A. B. & Furevik, T. in The Nordic Seas: An Integrated Perspective (eds Drange, H., Dokken, T. M., Furevik, T., Gerdes, R. & Berger, W.) 89–104 (Geophysical Monograph Series 158, American Geophysical Union, 2005).

    Google Scholar 

  27. Käse, R. H., Serra, N., Köhl, A. & Stammer, D. Mechanisms for the variability of dense water pathways in the Nordic Seas. J. Geophys. Res. 114, C01013 (2009).

    Article  Google Scholar 

  28. Mauritzen, C. Production of dense overflow waters feeding the North Atlantic across the Greenland–Scotland Ridge. Part 2: An inverse model. Deep-Sea Res. I 43, 807–835 (1996).

    Article  Google Scholar 

  29. Guemas, V. & Salas-Mélia, D. Simulation of the Atlantic Meridional Overturning Circulation in an Atmosphere-Ocean Global Coupled Model. Part I: A mechanism governing the variability of ocean convection in a preindustrial experiment. Clim. Dyn. 31, 29–48 (2007).

    Article  Google Scholar 

  30. Rudels, B. et al. The interaction between waters from the Arctic Ocean and the Nordic Seas north of Fram Strait and along the East Greenland current: Results from the Arctic Ocean-02 Oden expedition. J. Mar. Syst. 55, 1–30 (2005).

    Article  Google Scholar 

Download references

Acknowledgements

This research was supported by the Norwegian Research Council through the projects ProClim, POCAHONTAS, BIAC and NorClim. The data were provided by the Marine Research Institute, Iceland; Institute of Marine Research, Norway; the Faroese Fisheries Laboratory; Geophysical Institute, University of Bergen, Norway; and the Arctic and Antarctic Research Institute, Russia, through the NISE project. The authors are grateful for discussions with numerous colleagues, particularly P. E. Isachsen, J. Lilly, K. Lygre, K. Oliver, Ø. Skagseth and D. J. Steinskog. This is publication No. A225 from the Bjerknes Centre for Climate Research.

Author information

Authors and Affiliations

  1. G. C. Rieber Climate Institute, Nansen Environmental and Remote Sensing Center, Thormøhlensgate 47, N-5006 Bergen, Norway

    Tor Eldevik, Jan Even Ø. Nilsen, Doroteaciro Iovino, Anne Britt Sandø & Helge Drange

  2. Bjerknes Centre for Climate Research, Allégaten 55, N-5007 Bergen, Norway

    Tor Eldevik, Jan Even Ø. Nilsen, Doroteaciro Iovino, K. Anders Olsson, Anne Britt Sandø & Helge Drange

  3. Department of Chemistry, Göteborg University, SE-412 96 Göteborg, Sweden

    K. Anders Olsson

  4. Geophysical Institute, University of Bergen, Allégaten 70, N-5007 Bergen, Norway

    Helge Drange

Authors
  1. Tor Eldevik
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Jan Even Ø. Nilsen
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Doroteaciro Iovino
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. K. Anders Olsson
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Anne Britt Sandø
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Helge Drange
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Tor Eldevik.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Eldevik, T., Nilsen, J., Iovino, D. et al. Observed sources and variability of Nordic seas overflow. Nature Geosci 2, 406–410 (2009). https://doi.org/10.1038/ngeo518

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/ngeo518

This article is cited by

Search

Advanced search

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