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| Titel |
Optimal surface salinity perturbations of the meridional overturning circulation |
| VerfasserIn |
F. Sévellec, T. Huck, J. Vialard, A. V. Fedorov |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021855
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| Zusammenfassung |
| Recent observations and modeling studies have stressed the influence of sea surface
salinity (SSS) perturbations on the North Atlantic circulation. To investigate this
question, Generalized Stability Analyses (GSAs) are performed in a hierarchy of ocean
circulation model (going from a 2D latitude-depth model to a ocean general circulation
model in a realistic global configuration). In the GSAs, the optimality is defined with
respect to the meridional overturning circulation intensity. The influence of the
large scale meridional gradient of SSS anomaly located in the North Atlantic is
highlight in every models. Although the steady states are asymptotically stable in every
experiments, the models are able to generate some transient growth due to optimal initial
perturbation of the SSS or variability due to optimal stochastic perturbation of the
SSS.
In the ocean general circulation model (OPA), an optimal mechanism leading to a
transient growth of the meridional overturning circulation is described. The transient
growth appears for a delay of 10.5Â yr after the perturbation by the optimal initial
SSS anomaly. This optimal initial anomaly is located north of 50-N. The transient
growth mechanism shows the importance of the large scale zonal gradient of the
mean temperature in the North Atlantic. The optimal surface salinity perturbations
studied herein yield upper bounds on the intensity of the response in meridional
overturning circulation. Using typical amplitudes of the Great Salinity Anomaly,
we find roughly an 11% reduction in the strength of the mean circulation in the
model. |
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