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| Titel |
Assimilation of Earth rotation parameters into a global ocean model: excitation of polar motion |
| VerfasserIn |
J. Saynisch, M. Wenzel, J. Schröter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 18, no. 5 ; Nr. 18, no. 5 (2011-09-08), S.581-585 |
| Datensatznummer |
250013965
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| Publikation (Nr.) |
 copernicus.org/npg-18-581-2011.pdf |
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| Zusammenfassung |
| The oceanic contribution to Earth rotation anomalies can be
manifold. Possible causes are a change of total ocean mass, changes in
current speed or location and changes in mass distribution. To derive
the governing physical mechanisms of oceanic Earth rotation excitation
we assimilate Earth rotation observations with a global circulation
ocean model. Before assimilation, observations of length of day and
polar motion were transformed into estimates of ocean angular
momentum. By using the adjoint 4D-VAR assimilation method we were
able to reproduce these estimated time series. Although length of day
was assimilated simultaneously the analysis in this paper focuses on
the oceanic polar motion generation. Our results show that changes in
mass distribution and currents contribute to oceanic polar motion
generation. Both contributions are highly correlated and show similar
amplitudes. The changes in the model done by the assimilation
procedure could be related to changes in the atmospheric forcing.
Since for geometrical reasons the change of total ocean mass does not
project on polar motion, we conclude that the polar motion is mainly
generated by a geostrophic response to atmospheric momentum
forcing. In geostrophic currents mass displacement and current speed
entail each other. This way the large similarity of mass and current
generated ocean angular momentum can be explained. |
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