• Barsugli, J. J., and D. S. Battisti, 1998: The basic effects of atmosphere–ocean thermal coupling on midlatitude variability. J. Atmos. Sci., 55 , 477493.

    • Search Google Scholar
    • Export Citation
  • Cayan, D. R., 1992a: Latent and sensible heat flux anomalies over the northern oceans: Driving the sea surface temperature. J. Phys. Oceanogr., 22 , 859881.

    • Search Google Scholar
    • Export Citation
  • Cayan, D. R., 1992b: Latent and sensible heat flux anomalies over the northern oceans: The connection to monthly atmospheric circulation. J. Climate, 5 , 354369.

    • Search Google Scholar
    • Export Citation
  • Chen, F., and M. Ghil, 1996: Interdecadal variability in a hybrid coupled ocean–atmosphere model. J. Phys. Oceanogr., 26 , 15611578.

    • Search Google Scholar
    • Export Citation
  • Cheng, W., R. Bleck, and C. Rooth, 2004: Multi-decadal thermohaline variability in an ocean-atmosphere general circulation model. Climate Dyn., 22 , 573590.

    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., and R. J. Greatbatch, 2000: Multidecadal thermohaline circulation variability driven by atmospheric surface flux forcing. J. Climate, 13 , 14811495.

    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., and M. E. Mann, 2000: Observed and simulated multidecadal variability in the Northern Hemisphere. Climate Dyn., 16 , 661676.

    • Search Google Scholar
    • Export Citation
  • Delworth, T. L., S. Manabe, and R. J. Stouffer, 1993: Interdecadal variations of the thermohaline circulation in a coupled ocean–atmosphere model. J. Climate, 6 , 19932011.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., 2006: Interaction of SST modes in the North Atlantic Ocean. J. Phys. Oceanogr., 36 , 286299.

  • Dijkstra, H. A., and A. von der Heydt, 2007: Localization of multidecadal variability. Part II: Spectral origin of multidecadal modes. J. Phys. Oceanogr., 37 , 24152428.

    • Search Google Scholar
    • Export Citation
  • Dijkstra, H. A., L. A. te Raa, M. Schmeits, and J. Gerrits, 2006: On the physics of the Atlantic Multidecadal Oscillation. Ocean Dyn., 56 , 3650.

    • Search Google Scholar
    • Export Citation
  • Dong, B., and R. T. Sutton, 2005: Mechanism of interdecadal thermohaline circulation variability in a coupled ocean–atmosphere GCM. J. Climate, 18 , 11171135.

    • Search Google Scholar
    • Export Citation
  • Eden, C., and T. Jung, 2001: North Atlantic interdecadal variability: Oceanic response to the North Atlantic Oscillation (1865–1997). J. Climate, 14 , 676691.

    • Search Google Scholar
    • Export Citation
  • Enfield, D. B., A. M. Mestas-Nuñez, and P. J. Trimble, 2001: The Atlantic multidecadal oscillation and its relation to rainfall and river flows in the continental U.S. Geophys. Res. Lett., 28 , 20772080.

    • Search Google Scholar
    • Export Citation
  • Ghil, M., and Coauthors, 2002: Advanced spectral methods for climatic time series. Rev. Geophys., 40 , 1003. doi:10.1029/2000RG000092.

  • Greatbatch, R. J., and S. Zhang, 1995: An interdecadal oscillation in an idealized ocean basin forced by constant heat flux. J. Climate, 8 , 8191.

    • Search Google Scholar
    • Export Citation
  • Griffies, S. M., and E. Tziperman, 1995: A linear thermohaline oscillator driven by stochastic atmospheric forcing. J. Climate, 8 , 24402453.

    • Search Google Scholar
    • Export Citation
  • Grosfeld, K., G. Lohmann, N. Rimbu, K. Fraedrich, and F. Lunkeit, 2007: Atmospheric multidecadal variation in the North Atlantic realm: Proxy data, observations, and atmospheric circulation model studies. Climate Past, 3 , 3950.

    • Search Google Scholar
    • Export Citation
  • Huck, T., A. C. de Verdière, and A. J. Weaver, 1999: Interdecadal variability of the thermohaline circulation in box-ocean models forced by fixed surface fluxes. J. Phys. Oceanogr., 29 , 865892.

    • Search Google Scholar
    • Export Citation
  • Jungclaus, J. H., H. Haak, M. Latif, and U. Mikolajewicz, 2005: Arctic–North Atlantic interactions and multidecadal variability of the meridional overturning circulation. J. Climate, 18 , 40134031.

    • Search Google Scholar
    • Export Citation
  • Kerr, R. A., 2000: A North Atlantic climate pacemaker for the centuries. Science, 288 , 19841986.

  • Kushnir, Y., 1994: Interdecadal variations in North Atlantic sea surface temperature and associated atmospheric conditions. J. Climate, 7 , 141157.

    • Search Google Scholar
    • Export Citation
  • Luterbacher, J., and Coauthors, 2002: Extending North Atlantic Oscillation reconstructions back to 1500. Atmos. Sci. Lett., 2 , 114124.

    • Search Google Scholar
    • Export Citation
  • Pacanowski, R. C., and S. M. Griffies, 2000: MOM 3.0 manual. [Available online at http://www.gfd1.gov/~smg/MOM/web/guide_parent/guide_parent.html.].

    • Search Google Scholar
    • Export Citation
  • Saravanan, R., and J. C. McWilliams, 1997: Stochasticity and spatial resonance in interdecadal climate fluctuations. J. Climate, 10 , 22992320.

    • Search Google Scholar
    • Export Citation
  • Saravanan, R., and J. C. McWilliams, 1998: Advective ocean–atmosphere interaction: An analytical stochastic model with implications for decadal variability. J. Climate, 11 , 165188.

    • Search Google Scholar
    • Export Citation
  • te Raa, L. A., and H. A. Dijkstra, 2002: Instability of the thermohaline ocean circulation on interdecadal timescales. J. Phys. Oceanogr., 32 , 138160.

    • Search Google Scholar
    • Export Citation
  • te Raa, L. A., and H. A. Dijkstra, 2003: Modes of internal thermohaline variability in a single-hemispheric ocean basin. J. Mar. Res., 61 , 491516.

    • Search Google Scholar
    • Export Citation
  • te Raa, L. A., J. Gerrits, and H. A. Dijkstra, 2004: Identification of the mechanism of interdecadal variablity in the North Atlantic Ocean. J. Phys. Oceanogr., 34 , 27922807.

    • Search Google Scholar
    • Export Citation
  • von der Heydt, A., and H. A. Dijkstra, 2007: Localization of multidecadal variability. Part I: Cross-equatorial transport and interbasin exchange. J. Phys. Oceanogr., 37 , 24012414.

    • Search Google Scholar
    • Export Citation
  • Winton, M., and E. S. Sarachik, 1993: Thermohaline oscillations induced by strong steady salinity forcing of general circulation models. J. Phys. Oceanogr., 23 , 13891410.

    • Search Google Scholar
    • Export Citation
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Noise-Induced Multidecadal Variability in the North Atlantic: Excitation of Normal Modes

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  • 1 Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, Netherlands
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Abstract

In this paper it is proposed that the stochastic excitation of a multidecadal internal ocean mode is at the origin of the multidecadal sea surface temperature variability in the North Atlantic. The excitation processes of the spatial sea surface temperature pattern associated with this multidecadal mode within an idealized three-dimensional model are studied by adding noise to the surface heat flux forcing. In the regime where the internal mode is damped, the amplitude of its sea surface temperature pattern depends on the type of noise forcing applied. While the mode is weakly excited by white noise, only the introduction of spatial and temporal coherence in the forcing, with characteristics of the North Atlantic Oscillation in particular, causes the amplitude of the variability to increase to levels comparable to those observed. Within this idealized model the physical mechanism of the excitation can be determined: the presence of the noise rectifies the background state and consequently changes the growth factor of the internal mode.

Corresponding author address: Leela Frankcombe, Institute for Marine and Atmospheric Research, Department of Physics and Astronomy, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands. Email: l.m.frankcombe@uu.nl

Abstract

In this paper it is proposed that the stochastic excitation of a multidecadal internal ocean mode is at the origin of the multidecadal sea surface temperature variability in the North Atlantic. The excitation processes of the spatial sea surface temperature pattern associated with this multidecadal mode within an idealized three-dimensional model are studied by adding noise to the surface heat flux forcing. In the regime where the internal mode is damped, the amplitude of its sea surface temperature pattern depends on the type of noise forcing applied. While the mode is weakly excited by white noise, only the introduction of spatial and temporal coherence in the forcing, with characteristics of the North Atlantic Oscillation in particular, causes the amplitude of the variability to increase to levels comparable to those observed. Within this idealized model the physical mechanism of the excitation can be determined: the presence of the noise rectifies the background state and consequently changes the growth factor of the internal mode.

Corresponding author address: Leela Frankcombe, Institute for Marine and Atmospheric Research, Department of Physics and Astronomy, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands. Email: l.m.frankcombe@uu.nl

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