Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean
<jats:title>Abstract</jats:title><jats:p>Broadband measurements of the internal wavefield will help to unlock an understanding of the energy cascade within the oceanic realm. However, there are challenges in acquiring observations with sufficient spatial resolution, especially in h...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/254202 2024-02-04T10:04:32+01:00 Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean Falder, M White, NJ Caulfield, CP 2016 application/pdf https://www.repository.cam.ac.uk/handle/1810/254202 English eng eng American Meteorological Society http://dx.doi.org/10.1175/jpo-d-15-0140.1 Journal of Physical Oceanography https://www.repository.cam.ac.uk/handle/1810/254202 Turbulence Diapycnal mixing Internal waves Circulation/ Dynamics Article 2016 ftunivcam 2024-01-11T23:28:52Z <jats:title>Abstract</jats:title><jats:p>Broadband measurements of the internal wavefield will help to unlock an understanding of the energy cascade within the oceanic realm. However, there are challenges in acquiring observations with sufficient spatial resolution, especially in horizontal dimensions. Seismic reflection profiling can achieve a horizontal and vertical resolution of order meters. It is suitable for imaging thermohaline fine structure on scales that range from tens of meters to hundreds of kilometers. This range straddles the transition from internal wave to turbulent regimes. Here, the authors analyze an 80-km-long seismic image from the Falkland Plateau and calculate vertical displacement spectra of tracked reflections. First, they show that these spectra are consistent with the Garrett–Munk model at small horizontal wavenumbers (i.e., <jats:italic>k</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> ≲ 3 × 10<jats:sup>−3</jats:sup> cpm). There is a transition to stratified turbulence at larger wavenumbers (i.e., <jats:italic>k</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> ≳ 2 × 10<jats:sup>−1</jats:sup> cpm). This transition occurs at length scales that are significantly larger than the Ozmidov length scale above which stratification is expected to modify isotropic Kolmogorov turbulence. Second, the authors observe a rapid onset of this stratified turbulence over a narrow range of length scales. This onset is consistent with a characteristic energy injection scale of stratified turbulence with a forward cascade toward smaller scales through isotropic turbulence below the Ozmidov length scale culminating in microscale dissipation. Finally, they estimate the spatial pattern of diapycnal diffusivity and show that the existence of an injection scale can increase these estimates by a factor of 2.</jats:p> M.F. is supported by the Department of Earth ... Article in Journal/Newspaper South Atlantic Ocean Apollo - University of Cambridge Repository Falkland Plateau ENVELOPE(-50.000,-50.000,-51.000,-51.000) Munk ENVELOPE(-95.993,-95.993,55.979,55.979) |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
Turbulence Diapycnal mixing Internal waves Circulation/ Dynamics |
spellingShingle |
Turbulence Diapycnal mixing Internal waves Circulation/ Dynamics Falder, M White, NJ Caulfield, CP Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
topic_facet |
Turbulence Diapycnal mixing Internal waves Circulation/ Dynamics |
description |
<jats:title>Abstract</jats:title><jats:p>Broadband measurements of the internal wavefield will help to unlock an understanding of the energy cascade within the oceanic realm. However, there are challenges in acquiring observations with sufficient spatial resolution, especially in horizontal dimensions. Seismic reflection profiling can achieve a horizontal and vertical resolution of order meters. It is suitable for imaging thermohaline fine structure on scales that range from tens of meters to hundreds of kilometers. This range straddles the transition from internal wave to turbulent regimes. Here, the authors analyze an 80-km-long seismic image from the Falkland Plateau and calculate vertical displacement spectra of tracked reflections. First, they show that these spectra are consistent with the Garrett–Munk model at small horizontal wavenumbers (i.e., <jats:italic>k</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> ≲ 3 × 10<jats:sup>−3</jats:sup> cpm). There is a transition to stratified turbulence at larger wavenumbers (i.e., <jats:italic>k</jats:italic><jats:sub><jats:italic>x</jats:italic></jats:sub> ≳ 2 × 10<jats:sup>−1</jats:sup> cpm). This transition occurs at length scales that are significantly larger than the Ozmidov length scale above which stratification is expected to modify isotropic Kolmogorov turbulence. Second, the authors observe a rapid onset of this stratified turbulence over a narrow range of length scales. This onset is consistent with a characteristic energy injection scale of stratified turbulence with a forward cascade toward smaller scales through isotropic turbulence below the Ozmidov length scale culminating in microscale dissipation. Finally, they estimate the spatial pattern of diapycnal diffusivity and show that the existence of an injection scale can increase these estimates by a factor of 2.</jats:p> M.F. is supported by the Department of Earth ... |
format |
Article in Journal/Newspaper |
author |
Falder, M White, NJ Caulfield, CP |
author_facet |
Falder, M White, NJ Caulfield, CP |
author_sort |
Falder, M |
title |
Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
title_short |
Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
title_full |
Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
title_fullStr |
Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
title_full_unstemmed |
Seismic imaging of rapid onset of stratified turbulence in the South Atlantic Ocean |
title_sort |
seismic imaging of rapid onset of stratified turbulence in the south atlantic ocean |
publisher |
American Meteorological Society |
publishDate |
2016 |
url |
https://www.repository.cam.ac.uk/handle/1810/254202 |
long_lat |
ENVELOPE(-50.000,-50.000,-51.000,-51.000) ENVELOPE(-95.993,-95.993,55.979,55.979) |
geographic |
Falkland Plateau Munk |
geographic_facet |
Falkland Plateau Munk |
genre |
South Atlantic Ocean |
genre_facet |
South Atlantic Ocean |
op_relation |
https://www.repository.cam.ac.uk/handle/1810/254202 |
_version_ |
1789973078555492352 |