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Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic

Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic
Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic
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% confidence interval. In ECCO-GODAE, we find that the observed and simulated MOC show a significant correlation within the 99% confidence interval. To investigate the contribution of the different transport components, the MOC is decomposed into Florida Current, Ekman and mid-ocean 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.
1812-0792
575-589
Baehr, J.
1606627f-1d88-4046-808f-030b627710cb
Cunningham, S.
07f1bd78-d92f-478b-a016-b92f530142c3
Haak, H.
a87ebbdd-58bf-4585-8d8b-fa69538e3893
Heimbach, P.
a5fd5b9f-8209-4c28-a064-729c30ba8a29
Kanzow, T.
ede4d92e-c4b2-48d0-83bf-a03f881aa819
Marotzke, J.
6047bfd1-68a3-4abe-95ce-e1df9a56ce76
Baehr, J.
1606627f-1d88-4046-808f-030b627710cb
Cunningham, S.
07f1bd78-d92f-478b-a016-b92f530142c3
Haak, H.
a87ebbdd-58bf-4585-8d8b-fa69538e3893
Heimbach, P.
a5fd5b9f-8209-4c28-a064-729c30ba8a29
Kanzow, T.
ede4d92e-c4b2-48d0-83bf-a03f881aa819
Marotzke, J.
6047bfd1-68a3-4abe-95ce-e1df9a56ce76

Baehr, J., Cunningham, S., Haak, H., Heimbach, P., Kanzow, T. and Marotzke, J. (2009) Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic. Ocean Science, 5 (4), 575-589.

Record type: Article

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% confidence interval. In ECCO-GODAE, we find that the observed and simulated MOC show a significant correlation within the 99% confidence interval. To investigate the contribution of the different transport components, the MOC is decomposed into Florida Current, Ekman and mid-ocean 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.

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Published date: 2009

Identifiers

Local EPrints ID: 73118
URI: https://eprints.soton.ac.uk/id/eprint/73118
ISSN: 1812-0792
PURE UUID: 00c61c8d-29d4-4960-8aee-8b1cc0eab69e

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Date deposited: 01 Mar 2010
Last modified: 19 Jul 2019 23:41

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Contributors

Author: J. Baehr
Author: S. Cunningham
Author: H. Haak
Author: P. Heimbach
Author: T. Kanzow
Author: J. Marotzke

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