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| Titel |
Observed mesoscale eddy sea surface temperature imprints |
| VerfasserIn |
Ute Hausmann, Arnaud Czaja, Dudley Chelton |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052016
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| Zusammenfassung |
| A robust observational estimate of mesoscale eddy sea surface temperature (SST) imprints,
central to mesoscale heat transports and eddy-atmosphere coupling, is provided for the
Southern Ocean by analysing the relationship between satellite microwave SST and
independent multi-altimeter sea surface height (SSH) observations, both at fixed-location and
by directly following propagating mesoscale eddies based on automated tracking of their SSH
anomalies.
At fixed location, SST variability is observed to feature narrow bands of enhanced mesoscale
control anchored at major Antarctic Circumpolar Current (ACC) fronts, where intense eddies
effectively stir surface isotherms. Large-scale processes, that dominate variability in the
adjacent subtropical gyre interiors, are found to be non-negligible even here. Following
eddies’ tracks allows to detect transient mesoscale SST imprints that clearly stand out from
this large-scale background even in quiet interiors.
The track-following analysis moreover reveals robust westward phase-shifts of eddies’ SST
anomalies with respect to their rotating cores. In energetic ACC regions the observed intense
warm-top anticyclones and cold-top cyclones are only nearly in-phase, whereas in
quiet regions weaker SST signatures are almost in quadrature with eddies’ SSH.
Consequentially propagating eddies flux heat poleward in the mixed-layer over a
broad range of Southern Ocean regimes, with the ratio of rotational to divergent
transports increasing towards energetic ACC regions. A composite eddy, typical of ACC
conditions, is shown to transport ~ 1012 W poleward in the mixed layer, an order of
magnitude more than a typical eddy originating in the quiet regions. Whereas these local,
baroclinic wave-type heat transports, consistent with the diffusive view, provide a
complete picture for quiet interiors, scalings suggest that across major ACC fronts an
additional non-local eddy heat transport mechanism is of zero-order importance. |
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