Journal cover Journal topic
Earth System Dynamics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 3.769 IF 3.769
  • IF 5-year value: 4.522 IF 5-year
    4.522
  • CiteScore value: 4.14 CiteScore
    4.14
  • SNIP value: 1.170 SNIP 1.170
  • SJR value: 2.253 SJR 2.253
  • IPP value: 3.86 IPP 3.86
  • h5-index value: 26 h5-index 26
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 22 Scimago H
    index 22
Volume 5, issue 1
Earth Syst. Dynam., 5, 103-115, 2014
https://doi.org/10.5194/esd-5-103-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Earth Syst. Dynam., 5, 103-115, 2014
https://doi.org/10.5194/esd-5-103-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Feb 2014

Research article | 20 Feb 2014

The role of the North Atlantic overturning and deep ocean for multi-decadal global-mean-temperature variability

C. F. Schleussner1,2, J. Runge1,3, J. Lehmann1,2, and A. Levermann1,2 C. F. Schleussner et al.
  • 1Potsdam Institute for Climate Impact Research, Telegrafenberg A62, 14473 Potsdam, Germany
  • 2Physics Institute, Potsdam University, Potsdam, Germany
  • 3Department of Physics, Humboldt University, Berlin, Germany

Abstract. Earth's climate exhibits internal modes of variability on various timescales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC), Northern Hemisphere sea-ice extent and global mean temperature (GMT) in an ensemble of CMIP5 models under control conditions. We report an inter-annual GMT variability of about ±0.1° C originating solely from natural variability in the model ensemble. By decomposing the GMT variance into contributions of the AMOC and Northern Hemisphere sea-ice extent using a graph-theoretical statistical approach, we find the AMOC to contribute 8% to GMT variability in the ensemble mean. Our results highlight the importance of AMOC sea-ice feedbacks that explain 5% of the GMT variance, while the contribution solely related to the AMOC is found to be about 3%. As a consequence of multi-decadal AMOC variability, we report substantial variations in North Atlantic deep-ocean heat content with trends of up to 0.7 × 1022 J decade−1 that are of the order of observed changes over the last decade and consistent with the reduced GMT warming trend over this period. Although these temperature anomalies are largely density-compensated by salinity changes, we find a robust negative correlation between the AMOC and North Atlantic deep-ocean density with density lagging the AMOC by 5 to 11 yr in most models. While this would in principle allow for a self-sustained oscillatory behavior of the coupled AMOC–deep-ocean system, our results are inconclusive about the role of this feedback in the model ensemble.

Publications Copernicus
Download
Citation
Share