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| Titel |
Seismic imaging of a thermohaline staircase in the western tropical North Atlantic |
| VerfasserIn |
I. Fer, P. Nandi, W. S. Holbrook, R. W. Schmitt, P. Páramo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 6, no. 3 ; Nr. 6, no. 3 (2010-07-02), S.621-631 |
| Datensatznummer |
250003577
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| Publikation (Nr.) |
 copernicus.org/os-6-621-2010.pdf |
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| Zusammenfassung |
| Multichannel seismic data acquired in the Lesser Antilles in the western
tropical North Atlantic indicate that the seismic reflection method has
imaged an oceanic thermohaline staircase. Synthetic acoustic modeling using measured density and sound speed profiles corroborates inferences from the seismic
data. In a small portion of the seismic image, laterally coherent, uniform layers are present at depths ranging from 550–700 m and have a separation of ~20 m, with thicknesses
increasing with depth. The reflection coefficient, a measure of the acoustic
impedance contrasts across these reflective interfaces, is one order of magnitude
greater than background noise. Hydrography sampled in previous surveys
suggests that the layers are a permanent feature of the region. Spectral analysis of layer horizons in the
thermohaline staircase indicates that internal wave activity is anomalously
low, suggesting weak internal wave-induced turbulence. Results
from two independent measurements, the application of a finescale
parameterization to observed high-resolution velocity profiles and direct
measurements of turbulent dissipation rate, confirm these low levels of
turbulence. The lack of internal wave-induced turbulence may allow for
the maintenance of the staircase or may be due to suppression by the double-diffusive convection within the staircase. Our observations show the potential for
seismic oceanography to contribute to an improved understanding of
occurrence rates and the geographical distribution of thermohaline
staircases, and should thereby improve estimates of vertical mixing rates
ascribable to salt fingering in the global ocean. |
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