The lateral coherence of a system of thermo-haline layers in the deep ocean

Elliott, A.J.; Howe, M.R.; Tait, R.I.

doi:10.1016/0011-7471(74)90067-9

Cited by 7 publications

(5 citation statements)

References 7 publications

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“…With small deviations the persistency lasts at least a day, mostly several days, and far beyond the buoyancy timescale. This suggests true layering and confirms previous observations [Elliott et al, 1974]. The layering in the examples of Figure 4 shows especially tight T values for dT/dz = 0 (Figures 4a and 4c).…”

Section: Nioz3 Temperature Variationssupporting

confidence: 91%

“…If produced via advection by horizontal inertial currents having amplitudes of ADCP‐observed 0.01–0.02 m s −1 , the NIOZ3‐observed T ( f ) would require horizontal gradients of d T /d x , y ≈ 10 −4 °C m −1 . Although we lack spatial information, this value seems too large for large‐scale ocean frontal phenomena and only occasionally some small‐scale, possibly internal wave‐induced, variations have been observed of the same size [ Elliott et al , 1974].…”

Section: Spectral Observationsmentioning

confidence: 99%

“…[10] If these layers are ''persistent'' in space and time, say larger than several km horizontally and present over more than one inertial period, as suggested from observations by Howe and Tait [1970] and Elliott et al [1974], they can support free internal waves up to the local buoyancy period T N = 2p/N. Here N = (Àgdlnr/dz) 1/2 denotes the buoyancy frequency, g the acceleration of gravity and r the density.…”

Section: Ctd Datamentioning

confidence: 99%

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High‐resolution open‐ocean temperature spectra

Haren

Gostiaux

2009

J. Geophys. Res.

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[1] Accurate (<1 mK) temperature sensors have been stiffly moored at $1450 m in the open Canary Basin for 1.5 years while sampling at 1 Hz. The sensors were in an area where regular density steps occur. In this article, we investigate the variability of internal waves in such ''steppy'' environment. The waves vertically move layers of persistent temperature gradients for particular temperatures. The frequency (s) spectra of temperature, and more clearly those of inferred vertical currents w, show an internal wave band IWB that extends from 0.97f < s < N t , where f denotes the inertial frequency or vertical Coriolis parameter. Transition frequency N t is higher than buoyancy frequency N, computed over large vertical scales Dz = O(100) m. The extension of IWB beyond the traditional bounds [f,N] is probably due to small-vertical -scale layering (Dz % 1 m). The associated weak stratification between such thin layers provides small-scale N s % 4f h , where f h denotes the horizontal Coriolis parameter. This minimum stable stratification N s is associated with tilting of vorticity away from gravity, which causes the subinertial spectral extent to 0.97f. Isothermal smoothing reveals details of coherent vertical internal wave and incoherent motions. The present w spectrum continuum of coherent IWB motions is not flat, as in previous near-surface observations, but linearly increases from s = f to a peak at s $ 0.8N. The coherence spectrum shows a weak, significant peak at approximately twice the local buoyancy frequency for 2.5 Dz 100 m. Instead of dominant mode 1, zero phase difference, observed in IWB across the 130 m of observations, these super-buoyancy motions show mode 2 dominance, p phase difference.

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Section: Nioz3 Temperature Variationssupporting

confidence: 91%

Section: Spectral Observationsmentioning

confidence: 99%

Section: Ctd Datamentioning

confidence: 99%

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High‐resolution open‐ocean temperature spectra

Haren

Gostiaux

2009

J. Geophys. Res.

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“…Evidence of thermohaline staircases associated with the MOW have been reported since the 70s 3,6 . In an early paper, Elliot et al 27 found homogeneous layers in the subtropical Northeast Atlantic at several depths. However, the authors found that the step-layers around 1500 m, just beneath the MOW, to be recurrent in widely spaced observed stations.…”

Section: Discussionmentioning

confidence: 98%

Acoustic imaging of stable double diffusion in the Madeira abyssal plain

Duarte,

Peliz,

Matias

et al. 2024

Preprint

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Sub-mesoscale and mesoscale (i.e., 1-10km and 10-200km, respectively) ocean processes are highly relevant for the understanding of global circulation, mixing of water masses and energy exchange between ocean layers. However, the processes happening at these scales are hard to be characterized using direct measurements of temperature and salinity. Direct measurements are obtained from vertical probes and/or autonomous vehicles, which, despite their high vertical resolution, are sparsely located in space and therefore unable to capture spatial details at these scales. Seismic oceanography (SO) data have been successful used to imaging and characterize the ocean at these spatial scales. These data represent indirect measurements of the ocean temperature and salinity along kilometric transects with high horizontal resolution (i.e., a near-synaptic view of the system under investigation), but lower vertical resolution when compared with direct observations. Despite its complex oceanographic setting, the Madeira Abyssal Plain is still largely uncharacterized due to the lack of direct observations. We show for the first time a comprehensive processing, modelling and interpretation of three 2-D seismic oceanography sections from this region. The data show coherent seismic reflection in space, depth and time and shed light into this oceanographic setting with an unprecedent horizontal resolution. The SO modelling and interpretation are combined with existing direct measurements and a quantitative method to correlate thermohaline staircases interpreted from conductivity-temperature-depth casts and seismic reflections is proposed. The results show the relatively stable presence of thermohaline staircases in simultaneously time and space between 1200–2000 m of water depth and their spatial variability and contribute to the generalization of SO in physical oceanography.

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“…Evidence of thermohaline staircases associated with the MOW have been reported since the 70s 3 , 7 . In an early paper, Elliot et al 31 found homogeneous layers in the subtropical Northeast Atlantic at several depths. However, the authors found that the step-layers around 1500 m, just beneath the MOW, to be recurrent in widely spaced observed stations.…”

Section: Discussionmentioning

confidence: 98%

Acoustic imaging of stable double diffusion in the Madeira abyssal plain

Duarte,

Peliz,

Matias

et al. 2024

Sci Rep

View full text Add to dashboard Cite

Sub-mesoscale and mesoscale (i.e., 1–10 km and 10–200 km, respectively) ocean processes are highly relevant for the understanding of global circulation, mixing of water masses and energy exchange between ocean layers. However, the processes happening at these scales are hard to be characterized using direct measurements of temperature and salinity. Direct measurements are obtained from vertical probes and/or autonomous vehicles, which, despite their high vertical resolution, are sparsely located in space and therefore unable to capture spatial details at these scales. Seismic oceanography (SO) data have been successfully used to imaging and characterize the ocean at these spatial scales. These data represent indirect measurements of the ocean temperature and salinity along kilometric transects with high horizontal resolution (i.e., a near-synaptic view of the system under investigation), but lower vertical resolution when compared with direct observations. Despite its complex oceanographic setting, the Madeira Abyssal Plain is still largely uncharacterized due to the lack of direct observations. We show for the first time a comprehensive processing, modelling and interpretation of three 2-D seismic oceanography sections from this region. The data show coherent seismic reflection in space, depth and time and shed light into this oceanographic setting with an unprecedent horizontal resolution. The SO modelling and interpretation are combined with existing direct measurements and a quantitative method to correlate thermohaline staircases interpreted from conductivity-temperature-depth casts and seismic reflections is proposed. The results show the relatively stable presence of thermohaline staircases in simultaneously time and space between 1200 and 2000 m of water depth and their spatial variability and contribute to the generalization of SO in physical oceanography.

show abstract

The lateral coherence of a system of thermo-haline layers in the deep ocean

Cited by 7 publications

References 7 publications

High‐resolution open‐ocean temperature spectra

High‐resolution open‐ocean temperature spectra

Acoustic imaging of stable double diffusion in the Madeira abyssal plain

Acoustic imaging of stable double diffusion in the Madeira abyssal plain

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