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The role of the North Atlantic overturning and deep-ocean for multi-decadal global-mean-temperature variability.
- Source :
- Earth System Dynamics Discussions; 2013, Vol. 4 Issue 2, p967-1003, 37p
- Publication Year :
- 2013
-
Abstract
- Earth's climate exhibits internal modes of variability on various time scales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC) in the control runs of an ensemble of CMIP5 models. By decomposing global- mean-temperature (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 deepocean heat content with trends of up to 0.7×10<superscript>22</superscript> J decade<superscript>-1</superscript> 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. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 21904995
- Volume :
- 4
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Earth System Dynamics Discussions
- Publication Type :
- Academic Journal
- Accession number :
- 93652030
- Full Text :
- https://doi.org/10.5194/esdd-4-967-2013