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| Titel |
Hyperbolicity in temperature and flow fields during the formation of a Loop Current ring |
| VerfasserIn |
M. H. M. Sulman, H. S. Huntley, B. L. Lipphardt, G. Jacobs, P. Hogan, A. D. Kirwan |
| 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 ; 20, no. 5 ; Nr. 20, no. 5 (2013-10-29), S.883-892 |
| Datensatznummer |
250086063
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| Publikation (Nr.) |
 copernicus.org/npg-20-883-2013.pdf |
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| Zusammenfassung |
| Loop Current rings (LCRs) are among the largest mesoscale eddies in the world
ocean. They arise when bulges formed by the Loop Current in the Gulf of
Mexico close off. The LCR formation process may take several weeks, and there
may be several separations and reattachments before final separation occurs.
It is well established that this period is characterized by a persistent
saddle point in the sea surface height field, as seen in both model and
satellite data. We present here a detailed study of this saddle region during
the formation of Eddy Franklin in 2010, over multiple days and at several
depths. Using a data-assimilating Gulf of Mexico implementation of the HYbrid
Coordinate Ocean Model (HYCOM), we compare the vertical structure of the
currents and temperature fields on 5 and 10 June 2010. Finite-time Lyapunov
exponents (FTLE) are computed from the surface down to 200 m to estimate the
location of relevant transport barriers. Several new features of the saddle
region associated with LCR formation are revealed: the ridges in the FTLE
fields are shown to be excellent surrogates for the manifolds delineating the
material flow structures with only slight degradation at depth. The
intersection of the ridges representing stable and unstable manifolds drops
nearly vertically through the water column at both times; remarkably, the
material boundary shapes are maintained even as they are advected. Moreover,
velocity stagnation points and saddle points in the temperature field are
consistently found near the intersections at all depths, and their geographic
positions are also nearly constant with depth. |
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