Climate Dynamics

, Volume 41, Issue 7–8, pp 2133–2144

A mechanism for Atlantic multidecadal variability in the Kiel Climate Model

  • Jin Ba
  • Noel S. Keenlyside
  • Wonsun Park
  • Mojib Latif
  • Ed Hawkins
  • Hui Ding
Article

DOI: 10.1007/s00382-012-1633-4

Cite this article as:
Ba, J., Keenlyside, N.S., Park, W. et al. Clim Dyn (2013) 41: 2133. doi:10.1007/s00382-012-1633-4

Abstract

Atlantic Multidecadal Variability (AMV) is investigated in a millennial control simulation with the Kiel Climate Model (KCM), a coupled atmosphere–ocean–sea ice model. An oscillatory mode with approximately 60 years period and characteristics similar to observations is identified with the aid of three-dimensional temperature and salinity joint empirical orthogonal function analysis. The mode explains 30 % of variability on centennial and shorter timescales in the upper 2,000 m of the North Atlantic. It is associated with changes in the Atlantic Meridional Overturning Circulation (AMOC) of ±1–2 Sv and Atlantic Sea Surface Temperature (SST) of ±0.2 °C. AMV in KCM results from an out-of-phase interaction between horizontal and vertical ocean circulation, coupled through Irminger Sea convection. Wintertime convection in this region is mainly controlled by salinity anomalies transported by the Subpolar Gyre (SPG). Increased (decreased) dense water formation in this region leads to a stronger (weaker) AMOC after 15 years, and this in turn leads to a weaker (stronger) SPG after another 15 years. The key role of salinity variations in the subpolar North Atlantic for AMV is confirmed in a 1,000 year long simulation with salinity restored to model climatology: No low frequency variations in convection are simulated, and the 60 year mode of variability is absent.

Keywords

Atlantic meridional overturning circulation AMOC Atlantic multidecadal variability AMV AMO Salinity 

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Jin Ba
    • 1
  • Noel S. Keenlyside
    • 2
  • Wonsun Park
    • 1
  • Mojib Latif
    • 1
  • Ed Hawkins
    • 3
  • Hui Ding
    • 1
  1. 1.GEOMAR Helmholtz Centre for Ocean Research KielKielGermany
  2. 2.Geophysical Institute and Bjerknes CentreUniversity of BergenBergenNorway
  3. 3.NCAS-Climate, Department of MeteorologyUniversity of ReadingReadingUK

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