Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic
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 seis...
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ftunivwyomingfig:oai:figshare.com:article/13678060 2023-05-15T17:31:36+02:00 Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic Ilker Fer Papia Nandi W. Steven Holbrook Raymond W. Schmitt Pedro Páramo 2010-07-02T00:00:00Z https://doi.org/10.5194/os-6-621-2010 https://figshare.com/articles/journal_contribution/Seismic_Imaging_of_a_Thermohaline_Staircase_in_the_Western_Tropical_North_Atlantic/13678060 unknown doi:10.5194/os-6-621-2010 https://figshare.com/articles/journal_contribution/Seismic_Imaging_of_a_Thermohaline_Staircase_in_the_Western_Tropical_North_Atlantic/13678060 CC BY 4.0 CC-BY Geology convection dissipation estimation method geographical distribution global ocean hydrography internal wave magnitude measurement method noise numerical model observational method oceanography seismic anisotropy seismic data seismic reflection spectral analysis survey thermohaline circulation turbulence velocity Text Journal contribution 2010 ftunivwyomingfig https://doi.org/10.5194/os-6-621-2010 2023-02-04T11:07:24Z 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 550-700m 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. Other Non-Article Part of Journal/Newspaper North Atlantic WyoScholar - University of Wyoming research repository Ocean Science 6 3 621 631 |
institution |
Open Polar |
collection |
WyoScholar - University of Wyoming research repository |
op_collection_id |
ftunivwyomingfig |
language |
unknown |
topic |
Geology convection dissipation estimation method geographical distribution global ocean hydrography internal wave magnitude measurement method noise numerical model observational method oceanography seismic anisotropy seismic data seismic reflection spectral analysis survey thermohaline circulation turbulence velocity |
spellingShingle |
Geology convection dissipation estimation method geographical distribution global ocean hydrography internal wave magnitude measurement method noise numerical model observational method oceanography seismic anisotropy seismic data seismic reflection spectral analysis survey thermohaline circulation turbulence velocity Ilker Fer Papia Nandi W. Steven Holbrook Raymond W. Schmitt Pedro Páramo Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
topic_facet |
Geology convection dissipation estimation method geographical distribution global ocean hydrography internal wave magnitude measurement method noise numerical model observational method oceanography seismic anisotropy seismic data seismic reflection spectral analysis survey thermohaline circulation turbulence velocity |
description |
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 550-700m 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. |
format |
Other Non-Article Part of Journal/Newspaper |
author |
Ilker Fer Papia Nandi W. Steven Holbrook Raymond W. Schmitt Pedro Páramo |
author_facet |
Ilker Fer Papia Nandi W. Steven Holbrook Raymond W. Schmitt Pedro Páramo |
author_sort |
Ilker Fer |
title |
Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
title_short |
Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
title_full |
Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
title_fullStr |
Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
title_full_unstemmed |
Seismic Imaging of a Thermohaline Staircase in the Western Tropical North Atlantic |
title_sort |
seismic imaging of a thermohaline staircase in the western tropical north atlantic |
publishDate |
2010 |
url |
https://doi.org/10.5194/os-6-621-2010 https://figshare.com/articles/journal_contribution/Seismic_Imaging_of_a_Thermohaline_Staircase_in_the_Western_Tropical_North_Atlantic/13678060 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_relation |
doi:10.5194/os-6-621-2010 https://figshare.com/articles/journal_contribution/Seismic_Imaging_of_a_Thermohaline_Staircase_in_the_Western_Tropical_North_Atlantic/13678060 |
op_rights |
CC BY 4.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/os-6-621-2010 |
container_title |
Ocean Science |
container_volume |
6 |
container_issue |
3 |
container_start_page |
621 |
op_container_end_page |
631 |
_version_ |
1766129263865495552 |