Insights from a 3‐D temperature sensors mooring on stratified ocean turbulence

Haren, Hans van; Cimatoribus, Andrea; Cyr, Frédéric; Gostiaux, Louis

doi:10.1002/2016gl068032

Cited by 10 publications

(9 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Oceanographic observations of internal tides entail in situ measurements of water temperature and current variations [e.g., Munk and Wunsch , ; Rudnick et al ., ; Garrett , ; van Haren et al ., ]. Modern satellite remote sensing of the sea surface conditions has confirmed the ubiquity of internal tides in the global oceans in relation to ocean‐bottom topography, and has further elucidated their significance with respect to ocean dynamics and energetics [ Ray and Mitchum , ; Egbert and Ray , ; Zhao , ].…”

Section: Introductionmentioning

confidence: 99%

Internal tides recorded at ocean bottom off the coast of Southeast Taiwan

et al. 2016

View full text Add to dashboard Cite

An ocean‐bottom experiment consisting of an array of four ocean‐bottom seismometers (OBS) was conducted off the coast of southeast Taiwan during May–July 2011. We develop comprehensive analyses of the space‐time kinematics of the tidal signals recorded in the compact high‐sensitivity temperature loggers (CHTL) and the OBS geophones at the ocean bottom with depths ranging from 1254 to 1610 m. The evidence suggests that internal tides are responsible for the recorded signals: baroclinic internal waves (mainly the M2 tide) are generated by barotropic tidal currents in the Luzon Strait. The internal tides exhibit gradual phase changing and irregularly fluctuating strength, leaving signatures in the CHTL as ambient temperature variations, signifying low‐mode wave motions within the stratified water layers; and in OBS geophones as intermittent “tremor” agitations, signifying high‐mode turbulent flows on the seafloor. The M2 internal tides across our array are found to propagate in the northeast direction at speeds ranging from 1 to 2+ m s−1. Furthermore, the internal tides are identified at the ocean‐bottom based on an operational hydrodynamic hindcast/forecast model. The simulations show good agreement with the observed temperature variation on the seafloor and substantiate the vertical velocity and displacement of the water parcel driven by the internal tides. The joint detection of the temperature and tremor signals provides further information about the interactions of internal tides with the seafloor topography and the associated energy dissipation. Our results elucidate the space‐time ubiquity of the internal tides at the ocean bottom, which is an important interface of dynamic oceanography.

show abstract

Section: Introductionmentioning

confidence: 99%

Internal tides recorded at ocean bottom off the coast of Southeast Taiwan

et al. 2016

View full text Add to dashboard Cite

show abstract

“…In contrast with the atmospheric observations of Frehlich et al (2008) and with 30-s sampled deep-ocean temperature spectra resolving just the stratified turbulence range (Bouruet-Aubertot et al, 2010), recent deep-ocean high-resolution 1-s sampled temperature spectra from a small-scale five-line 3D mooring array above steep topography demonstrated a two orders of magnitude wide inertial subrange N <  < roll-off with distinctly different small-range variability in the low-and high-frequency parts (van Haren et al, 2016). The distinction was not found in the smooth DNS-spectra (e.g., Augier et al, 2015;Maffioli, 2017).…”

mentioning

confidence: 67%

“…For the latter to occur one needs a large slope, with spatial scales exceeding those of the carrier wave. The internal tide has a horizontal scale O(1 km), which may explain why the small ridge-crest site does not exhibit shear-convection, but highly shear-induced turbulence mainly: Its horizontal spatial scales match those of the internal tide (van Haren et al, 2016). The convection is not necessarily horizontally bounded, but the indirect effects of the topography are the wave steepening and breaking, which is expected to vary over the wave's horizontal scales that set a natural boundary.…”

Section: General Discussion and Conclusionmentioning

confidence: 99%

Deep-ocean inertial subrange small bandwidth coherence and Ozmidov-frequency separation

Haren

2019

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

The inertial subrange of turbulence in a density stratified environment is the transition from internal waves to isotropic turbulence, but it is unclear how to interpret its extension to anisotropic 'stratified' turbulence. Knowledge about stratified turbulence is relevant for the dispersal of suspended matter in geophysical flows, such as in most of the ocean. For studying internal-wave-induced ocean-turbulence moored highresolution temperature (T-)sensors are used. Spectra from observations on episodic quasi-convective internal wave breaking above a steep slope of large seamount Josephine in the Northeast-Atlantic demonstrate an inertial subrange that can be separated in two parts: A large-scale part with relatively coherent portions adjacent to less coherent portions, and a small-scale part that is smoothly continuous (to within standard error). The separation is close to the Ozmidov frequency, and coincides with the transition from anisotropic/quasi-deterministic stratified turbulence to isotropic/stochastic inertial convective motions as inferred from a comparison of vertical and horizontal co-spectra. These observations contrast with T-sensor observations of shear-dominated internal wave breaking in an equally turbulent environment above the slope of a small Mid-Atlantic ridge-crest, which demonstrate a stochastic inertial subrange throughout.

show abstract

“…The similarity between the patterns in Figures 7a and 7b supports the interpretation of our observations in terms of partly standing waves. Figure 8 shows four consecutive hours of snapshots of the JCOPE-simulated temperature perturbation field detided by using the tide killer filter of Hanawa and Mitsudera (1985). Temperature perturbation is defined as deviation of the model temperature at each moment in time from the daily mean temperature.…”

Section: Journal Of Geophysical Research: Oceansmentioning

confidence: 99%

“…Internal ocean tides have been observed by satellite remote sensing of sea surface elevation (Egbert & Ray, ; Dushaw, ; Egbert & Ray, ; Zhao et al, ; Zhao, ) and moored measurement of oceanographic quantities (Garrett & St. Laurent, ; Kelly et al, ; Kunze et al, ; Martini et al, ; Munk & Wunsh, ; Nash et al, ; Rainville & Pinkel, ; Rudnick et al, ; van Haren et al, ). In contrast to these observations from above the sea surface and through water columns, attempts to detect internal tides from below (from the ocean bottom) are few.…”

Section: Introductionmentioning

confidence: 99%

Detection of Ocean Internal Tide Source Oscillations on the Slope of Aogashima Island, Japan

et al. 2019

View full text Add to dashboard Cite

Barotropic tidal currents over bottom topography force density surfaces to oscillate vertically and thereby to act as quasi‐stationary internal tide sources. Deploying a seafloor pressure gauge array with an aperture of 30 km for a year (2014–2015), we detected the low‐mode semidiurnal internal tidal waves propagating with a horizontal phase speed of ~1 m/s in the onshore and offshore directions over the array along the eastern slope of Aogashima Island, south of Japan. The amplitudes of the offshore propagating waves were greater than those of the onshore propagating waves, and both were positively correlated with the amplitudes of the local semidiurnal tide, which peaked in September and March. A tide‐resolving ocean circulation model (JCOPE‐T) well reproduced the observed onshore and offshore internal tidal wave propagation. The model indicated a standing wave region on the slope, where offshore propagating waves interact with standing waves locally pinned to the slope. Along the same profile over a distance of 100 km, we conducted seismic‐oceanographic analysis of the legacy multichannel seismic reflection data to retrieve vertical cross sections of the reflecting layers, which indicated sharp temperature changes in the ocean. Many of the slant reflecting layers were subparallel to the contour lines of the semidiurnal internal‐tide‐associated temperature anomalies in the JCOPE‐T model, suggesting a causal link between the fine reflection layering structure and the semidiurnal low‐mode internal tidal field.

show abstract

Insights from a 3‐D temperature sensors mooring on stratified ocean turbulence

Cited by 10 publications

References 21 publications

Internal tides recorded at ocean bottom off the coast of Southeast Taiwan

Internal tides recorded at ocean bottom off the coast of Southeast Taiwan

Deep-ocean inertial subrange small bandwidth coherence and Ozmidov-frequency separation

Detection of Ocean Internal Tide Source Oscillations on the Slope of Aogashima Island, Japan

Contact Info

Product

Resources

About