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Climate Dynamics

, Volume 36, Issue 5–6, pp 1107–1118 | Cite as

Reversed North Atlantic gyre dynamics in present and glacial climates

  • Marisa MontoyaEmail author
  • Andreas Born
  • Anders Levermann
Article

Abstract

The dynamics of the North Atlantic subpolar gyre (SPG) are assessed under present and glacial boundary conditions by investigating the SPG sensitivity to surface wind-stress changes in a coupled climate model. To this end, the gyre transport is decomposed in Ekman, thermohaline, and bottom transports. Surface wind-stress variations are found to play an important indirect role in SPG dynamics through their effect on water-mass densities. Our results suggest the existence of two dynamically distinct regimes of the SPG, depending on the absence or presence of deep water formation (DWF) in the Nordic Seas and a vigorous Greenland–Scotland ridge (GSR) overflow. In the first regime, the GSR overflow is weak and the SPG strength increases with wind-stress as a result of enhanced outcropping of isopycnals in the centre of the SPG. As soon as a vigorous GSR overflow is established, its associated positive density anomalies on the southern GSR slope reduce the SPG strength. This has implications for past glacial abrupt climate changes, insofar as these can be explained through latitudinal shifts in North Atlantic DWF sites and strengthening of the North Atlantic current. Regardless of the ultimate trigger, an abrupt shift of DWF into the Nordic Seas could result both in a drastic reduction of the SPG strength and a sudden reversal in its sensitivity to wind-stress variations. Our results could provide insight into changes in the horizontal ocean circulation during abrupt glacial climate changes, which have been largely neglected up to now in model studies.

Keywords

Atlantic Meridional Overturn Circulation Deep Water Formation North Atlantic Current Atlantic Meridional Overturn Circulation Strength Meridional Density Gradient 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Marisa Montoya
    • 1
    Email author
  • Andreas Born
    • 2
    • 3
  • Anders Levermann
    • 4
    • 5
  1. 1.Dpto. Astrofísica y Ciencias de la Atmósfera, Facultad de Ciencias FísicasUniversidad Complutense de Madrid, Ciudad UniversitariaMadridSpain
  2. 2.Bjerknes Centre for Climate ResearchBergenNorway
  3. 3.Geophysical InstituteUniversity of BergenBergenNorway
  4. 4.Earth System Analysis, Potsdam Institute for Climate Impact ResearchPotsdamGermany
  5. 5.Institute of PhysicsPotsdam UniversityPotsdamGermany

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