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www.ocean-sci-discuss.net/6/1333/2009/
doi:10.5194/osd-6-1333-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic
1Massachusetts Institute of Technology, Cambridge, MA, USA
2National Oceanography Centre, Southampton, UK
3Max Planck Institute for Meteorology, Hamburg, Germany
4National Oceanography Centre, Southampton, UK
*now at: Institute of Oceanography, KlimaCampus, University of Hamburg, Grindelberg 5, 20144 Hamburg, Germany
**now at: IFM-GEOMAR, Kiel, Germany
Abstract. Daily timeseries of the meridional overturning circulation (MOC) estimated from the UK/US RAPID/MOCHA array at 26.5° N in the Atlantic are used to evaluate the MOC as simulated in two global circulation models: (i) an 8-member ensemble of the coupled climate model ECHAM5/MPI-OM, and (ii) the ECCO-GODAE state estimate. In ECHAM5/MPI-OM, we find that the observed and simulated MOC have a similar variability and time-mean within the 99 percent confidence interval. In ECCO-GODAE, we find that the observed and simulated MOC show a significant correlation within the 99 percent confidence interval. To investigate the contribution of the different transport components, the MOC is decomposed into Florida Current, Ekman and upper mid-ocean geostrophic transports. In both models, the mid-ocean transport is closely approximated by the residual of the MOC minus Florida Current and Ekman transports. As the models conserve volume by definition, future comparisons of the RAPID/MOCHA mid-ocean transport should be done against the residual transport in the models. The similarity in the variance and the correlation between the RAPID/MOCHA, and respectively ECHAM5/MPI-OM and ECCO-GODAE MOC estimates at 26.5° N is encouraging in the context of estimating (natural) variability in climate simulations and its use in climate change signal-to-noise detection analyses. Enhanced confidence in simulated hydrographic and transport variability will require longer observational time series.
Discussion Paper (PDF, 1836 KB) Interactive Discussion (Closed, 4 Comments) Manuscript under review for OS
Citation: Baehr, J., Cunnningham, S., Haak, H., Heimbach, P., Kanzow, T., and Marotzke, J.: Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic, Ocean Sci. Discuss., 6, 1333-1367, doi:10.5194/osd-6-1333-2009, 2009. Bibtex EndNote Reference Manager XML
