Ocean Dynamics

, Volume 57, Issue 3, pp 223–235 | Cite as

Recent changes of the thermohaline circulation in the subpolar North Atlantic

  • Manfred BerschEmail author
  • Igor Yashayaev
  • Klaus Peter Koltermann


Time series of hydrographic sections in the northern North Atlantic from the period 1990 to 2004 are analyzed for changes in the characteristics and distribution of water masses that are involved in the thermohaline circulation (THC). During the 1990s, the North Atlantic Oscillation (NAO) alternates from a positive phase (strong westerlies) to a negative phase (weak westerlies). The reduced ocean heat loss confined the convection in the Labrador Sea to the upper 1,200 m, generating a new salinity minimum layer characterizing the Upper Labrador Sea Water (ULSW), and led to a warming and salinization of the older LSW below due to lateral mixing. The Lower LSW, formed in the first half of the 1990s, spread in the subpolar gyre and reached the Newfoundland and Irminger basins after about 1 to 2 years, where the associated isopycnal doming contributed to eastward frontal shifts in the upper layer. After 5 and 6 years, it arrived in the Iceland and West European basins, respectively. The collapse of the isopycnal dome in the Labrador Sea, associated with the drainage of the Lower LSW, resulted in a slowing of the cyclonic circulation of the subpolar gyre. This was accompanied in the upper layer by a westward shift of the southeastern extension of the gyre and a northward advection of warm and saline subtropical water in its eastern part, which finally reached the Labrador Sea after about 7 years. In the upper layer of the Labrador Sea, the advection of warm and saline water dominated over the heat loss to the atmosphere and the freshwater gain from melting ice and precipitation in the NAO-low period, so that no accumulation of freshwater but an increase of the heat and salt contents were observed, as in the whole eastern part of the subpolar gyre. Within 1 to 2 years after the drop of the NAO in the winter of 1995/1996, the Subarctic (Subpolar) Front shifted northward and westward north of about 50°N, favored by the retreat of the low-salinity tongue extending eastward from the southern Labrador Sea, and it shifted southward and eastward in the Newfoundland Basin. Therefore, the enhanced northward advection of subtropical waters in the northeastern North Atlantic is balanced by the enhanced southward advection of subarctic waters, including Lower LSW in the Newfoundland Basin, indicating a strong response of the gyre component of the THC.


Thermohaline circulation Subpolar North Atlantic Labrador Sea Water Subpolar gyre Subarctic Front North Atlantic Oscillation 



We thank the sailors, technicians, and scientists who were involved in the hydrographic measurements. Helpful discussions with Hendrik van Aken, Helmuth Haak, and Johann Jungclaus are appreciated. The study was supported by the Bundesministerium für Bildung und Forschung under grant no. 03F0377E and 03F0378A (CLIVAR-marin).


  1. Bacon S, Gould WJ, Jia Y (2003) Open-ocean convection in the Irminger Sea. Geophys Res Lett 30:1246CrossRefGoogle Scholar
  2. Beismann JO, Barnier B (2004) Variability of the meridional overturning circulation of the North Atlantic: sensitivity to overflows of dense water masses. Ocean Dyn 54:92–106CrossRefGoogle Scholar
  3. Bentsen M, Drange H, Furevik T, Zhou T (2004) Simulated variability of the Atlantic meridional overturning circulation. Clim Dyn 22:701–720CrossRefGoogle Scholar
  4. Bersch M (2002) North Atlantic Oscillation-induced changes of the upper layer circulation in the northern North Atlantic Ocean. J Geophys Res 107:3156CrossRefGoogle Scholar
  5. Bersch M, Meincke J, Sy A (1999) Interannual thermohaline changes in the northern North Atlantic 1991–1996. Deep-Sea Res II 46:55–75CrossRefGoogle Scholar
  6. Böning CW, Rhein M, Dengg J, Dorow C (2003) Modeling CFC inventories and formation rates of Labrador Sea Water. Geophys Res Lett 30:1050CrossRefGoogle Scholar
  7. Böning CW, Scheinert M, Dengg J, Biastoch A, Funk A (2006) Decadal variability of subpolar gyre transport and its reverberation in the North Atlantic overturning. Geophys Res Lett 33:L21S01CrossRefGoogle Scholar
  8. Centurioni LR, Gould WJ (2004) Winter conditions in the Irminger Sea observed with profiling floats. J Mar Res 62:313–336CrossRefGoogle Scholar
  9. Cunningham SA, Haine TW (1995) Labrador Sea Water in the eastern North Atlantic. Part I: a synoptic circulation inferred from a minimum in potential vorticity. J Phys Oceanogr 25:649–665CrossRefGoogle Scholar
  10. Cuny J, Rhines PB, Niiler PP, Bacon S (2002) Labrador Sea boundary currents and the fate of the Irminger Sea Water. J Phys Oceanogr 32:627–647CrossRefGoogle Scholar
  11. Curry RG, Mauritzen C (2005) Dilution of the northern North Atlantic Ocean in recent decades. Science 308:1772–1774CrossRefGoogle Scholar
  12. Curry RG, McCartney MS (2001) Ocean gyre circulation changes associated with the North Atlantic oscillation. J Phys Oceanogr 31:3374–3400CrossRefGoogle Scholar
  13. Curry RG, Dickson R, Yashayaev I (2003) A change in the freshwater balance of the Atlantic Ocean over the past four decades. Nature 426:826–829CrossRefGoogle Scholar
  14. Delworth TL, Dixon KW (2000) Implications of the recent trend in the Arctic/North Atlantic Oscillation for the North Atlantic thermohaline circulation. J Clim 13:3721–3727CrossRefGoogle Scholar
  15. Deser C, Holland M, Reverdin G, Timlin M (2002) Decadal variations in Labrador Sea ice cover and North Atlantic sea surface temperatures. J Geophys Res 107(C5):3035CrossRefGoogle Scholar
  16. Dickson RR, Lazier JRN, Meincke J, Rhines P, Swift J (1996) Longterm coordinated changes in the convective activity of the North Atlantic. Progr Oceanogr 38:241–295CrossRefGoogle Scholar
  17. Dooley HD, Martin JHA, Ellett DJ (1984) Abnormal hydrographic conditions in the Northeast Atlantic during the 1970s. Rapp P-V Reun Cons Int Explor Mer 185:179–187Google Scholar
  18. Eden C, Greatbatch RJ (2003) A damped decadal oscillation in the North Atlantic climate system. J Clim 16:443–460CrossRefGoogle Scholar
  19. Eden C, Jung T (2001) On the mechanism of the North Atlantic interdecadal variability. J Clim 14:676–691CrossRefGoogle Scholar
  20. Eden C, Willebrand J (2001) Mechanism of interannual to decadal variability of the North Atlantic circulation. J Clim 14:2266–2280CrossRefGoogle Scholar
  21. Esselborn S, Eden C (2001) Sea surface height changes in the North Atlantic Ocean related to the North Atlantic Oscillation. Geophys Res Lett 28:3473–3476CrossRefGoogle Scholar
  22. Faure V, Speer K (2005) Labrador Sea Water circulation in the northern North Atlantic Ocean. Deep-Sea Res II 52:565–581CrossRefGoogle Scholar
  23. Fischer J, Schott FA (2002) Labrador Sea Water tracked by profiling floats-from the boundary current into the open North Atlantic. J Phys Oceanogr 32:573–584CrossRefGoogle Scholar
  24. Flatau M, Talley L, Niiler PP (2003) The North Atlantic Oscillation, surface current velocities, and SST changes in the subpolar North Atlantic. J Clim 16:2355–2369CrossRefGoogle Scholar
  25. Frankignoul C, De Coetlogon G, Joyce TM, Dong S (2001) Gulf Stream variability and ocean-atmosphere interactions. J Phys Oceanogr 31:3516–3529CrossRefGoogle Scholar
  26. Grey SM, Haines K, Troccoli A (2000) A study of temperature changes in the upper North Atlantic: 1950–94. J Clim 13:2697–2711CrossRefGoogle Scholar
  27. Gulev SK, Barnier B, Knochel H, Molines JM, Cottet M (2003) Water mass transformation in the North Atlantic and its impact on the meridional circulation: insights from an ocean model forced by NCEP–NCAR reanalysis surface fluxes. J Clim 16:3085–3110CrossRefGoogle Scholar
  28. Häkkinen S (1999) Variability of the simulated meridional heat transport in the North Atlantic for the period 1951–1993. J Geophys Res 104:10991–11007CrossRefGoogle Scholar
  29. Häkkinen S (2002a) Freshening of the Labrador Sea surface waters in the 1990s: another great salinity anomaly? Geophys Res Lett 29:2232CrossRefGoogle Scholar
  30. Häkkinen S (2002b) Surface salinity variability in the northern North Atlantic during recent decades. J Geophys Res 107:8003CrossRefGoogle Scholar
  31. Häkkinen S, Rhines PB (2004) Decline of subpolar North Atlantic circulation during the 1990s. Science 304:555–559CrossRefGoogle Scholar
  32. Hansen DV, Bezdek HF (1996) On the nature of decadal anomalies in North Atlantic sea surface temperature. J Geophys Res 101:8749–8758CrossRefGoogle Scholar
  33. Hatun H, Sando AB, Drange H, Hansen B, Valdimarsson H (2005) Influence of the Atlantic subpolar gyre on the thermohaline circulation. Science 309:1841–1844CrossRefGoogle Scholar
  34. Holliday NP (2003) Air-sea interaction and circulation changes in the northeast Atlantic. J Geophys Res 108:3259CrossRefGoogle Scholar
  35. Houghton RW, Visbeck M (2002) Quasi-decadal salinity fluctuations in the Labrador Sea. J Phys Oceanogr 32:687–701CrossRefGoogle Scholar
  36. Hurrell JW (1995) Decadal trends in the North Atlantic oscillation: Regional temperatures and precipitation. Science 269:676–679CrossRefGoogle Scholar
  37. Hurrell JW, Kushnir Y, Ottersen G, Visbeck M (2003) An overview of the North Atlantic Oscillation. In: The North Atlantic oscillation: climatic significance and environmental impact. Geophys Monogr 134:1–35Google Scholar
  38. Joyce TM, Deser C, Spall MA (2000) The relation between decadal variability of subtropical mode water and the North Atlantic oscillation. J Clim 13:2550–2569CrossRefGoogle Scholar
  39. Khatiwala S, Schlosser P, Visbeck M (2002) Rates and mechanisms of water mass transformation in the Labrador Sea as inferred from tracer observations. J Phys Oceanogr 32:666–686CrossRefGoogle Scholar
  40. Koltermann KP, Sokov AV, Tereschenkov VP, Dobroliubov SA, Lorbacher K, Sy A (1999) Decadal changes in the thermohaline circulation of the North Atlantic. Deep-Sea Res II 46:109–138CrossRefGoogle Scholar
  41. Lavender KL, Davis RE, Owens WB (2000) Mid-depth recirculation observed in the interior Labrador and Irminger seas by direct velocity measurements. Nature 407:66–69CrossRefGoogle Scholar
  42. Lavender KL, Owens WB, Davis RE (2005) The mid-depth circulation of the subpolar North Atlantic Ocean as measured by subsurface floats. Deep-Sea Res I 52:767–785CrossRefGoogle Scholar
  43. Lazier JRN (1995) The salinity decrease in the Labrador Sea over the past thirty years. In: Natural climate variability on decade-to-century time scales. National Academy Press, WashingtonGoogle Scholar
  44. Lazier J, Hendry R, Clarke A, Yashayaev I, Rhines P (2002) Convection and restratification in the Labrador Sea, 1990–2000. Deep-Sea Res I 49:1819–1835CrossRefGoogle Scholar
  45. Levitus S (1989) Interpentadal variability of salinity in the upper 150 m of the North Atlantic Ocean, 1970–1974 versus 1955–1959. J Geophys Res 94:9679–9685CrossRefGoogle Scholar
  46. Levitus S, Antonov JI, Boyer TP, Stephens C (2000) Warming of the world ocean. Science 287:2225–2229CrossRefGoogle Scholar
  47. Marsh R (2000) Recent variability of the North Atlantic thermohaline circulation inferred from surface heat and freshwater fluxes. J Clim 13:3239–3260CrossRefGoogle Scholar
  48. Marsh R, de Cuevas BA, Coward AC, Bryden HL (2005) Thermohaline circulation at three key sections in the North Atlantic over 1985–2002. Geophys Res Lett 32:L10604CrossRefGoogle Scholar
  49. Marshall J, Johnson H, Goodman J (2001) A study of the interaction of the North Atlantic Oscillation with ocean circulation. J Clim 14:1399–1421CrossRefGoogle Scholar
  50. Nilsen JEO, Gao Y, Drange H, Furevik T, Bentsen M (2003) Simulated North Atlantic-Nordic Seas water mass exchanges in an isopycnic coordinate OGCM. Geophys Res Lett 30:1536CrossRefGoogle Scholar
  51. Paillet J, Arhan M, McCartney MS (1998) Spreading of Labrador Sea Water in the eastern North Atlantic. J Geophys Res 103:10223–10239CrossRefGoogle Scholar
  52. Pickart RS, Straneo F, Moore GWK (2003) Is Labrador Sea Water formed in the Irminger Basin? Deep-Sea Res I 50:23–52CrossRefGoogle Scholar
  53. Pollard RT, Read JF, Holliday NP, Leach H (2004) Water masses and circulation pathways through the Iceland Basin during Vivaldi 1996. J Geophys Res 109:C04004CrossRefGoogle Scholar
  54. Reverdin G, Verbrugge N, Valdimarsson H (1999) Upper ocean variability between Iceland and Newfoundland, 1993–1998. J Geophys Res 104:29599–29611CrossRefGoogle Scholar
  55. Reverdin G, Durand F, Mortensen J, Schott F, Valdimarsson H, Zenk W (2002) Recent changes in the surface salinity of the North Atlantic subpolar gyre. J Geophys Res 107:8010CrossRefGoogle Scholar
  56. Rhein M, Fischer J, Smethie WM, Smythe-Wright D, Weiss RF, Mertens C, Min DH, Fleischmann U, Putzka A (2002) Labrador Sea Water: pathways, CFC inventory, and formation rates. J Phys Oceanogr 32:648–665CrossRefGoogle Scholar
  57. Schott FA, Zantopp R, Stramma L, Dengler M, Fischer J, Wibaux M (2004) Circulation and deep-water export at the western exit of the subpolar North Atlantic. J Phys Oceanogr 34:817–843CrossRefGoogle Scholar
  58. Stramma L, Kieke D, Rhein M, Schott F, Yashayaev I, Koltermann KP (2004) Deep water changes at the western boundary of the subpolar North Atlantic during 1996 to 2001. Deep-Sea Res I 51:1033–1056Google Scholar
  59. Verbrugge N, Reverdin G (2003) Contribution of horizontal advection to the interannual variability of sea surface temperature in the North Atlantic. J Phys Oceanogr 33:964–978CrossRefGoogle Scholar
  60. Visbeck M, Chassignet EP, Curry RG, Delworth TL, Dickson RR, Krahmann G (2003) The ocean’s response to North Atlantic oscillation variability. In: The North Atlantic oscillation: climatic significance and environmental impact. Geophys Monogr 134:113–145Google Scholar
  61. Wunsch C (2002) What is the thermohaline circulation? Science 298:1179–1181CrossRefGoogle Scholar
  62. Yashayaev I, Bersch M, van Aken H, Clarke A (2004) A new study of the production, spreading and fate of the Labrador Sea Water in the subpolar North Atlantic. ASOF Newsl 2:20–22Google Scholar

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Manfred Bersch
    • 1
    Email author
  • Igor Yashayaev
    • 2
  • Klaus Peter Koltermann
    • 3
  1. 1.Institut für MeereskundeUniversität HamburgHamburgGermany
  2. 2.Bedford Institute of OceanographyDartmouthCanada
  3. 3.Bundesamt für Seeschifffahrt und HydrographieHamburgGermany

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