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Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic : Volume 6, Issue 3 (02/07/2010)

By Fer, I.

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Book Id: WPLBN0004020469
Format Type: PDF Article :
File Size: Pages 11
Reproduction Date: 2015

Title: Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic : Volume 6, Issue 3 (02/07/2010)  
Author: Fer, I.
Volume: Vol. 6, Issue 3
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Publication Date:
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications


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Schmitt, R. W., Holbrook, W. S., Fer, I., Páramo, P., & Nandi, P. (2010). Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic : Volume 6, Issue 3 (02/07/2010). Retrieved from

Description: Geophysical Institute, University of Bergen, Allégaten 70, 5007, Bergen, Norway. 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.

Seismic imaging of a thermohaline staircase in the western tropical North Atlantic

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