The relative effects of particles and turbulence on acoustic scattering from deep-sea hydrothermal vent plumes

Xu, Guangyu; Iorio, Daniela Di

doi:10.1121/1.3624816

Cited by 15 publications

(27 citation statements)

References 28 publications

(34 reference statements)

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“…Such methods have varied from backscattering of an acoustic pulse by small suspended particles [ Palmer , ; Palmer and Rona , ] or turbulent temperature fluctuations [ Ross and Lueck , ; Ostachev and Wilson , ] to the use of a Doppler effect to measure flow velocity and mean vertical velocity [ Jackson et al , ]. An alternative method, the acoustic scintillation from forward scattered signals, has been applied at the MEF [ Xu and Di Iorio , ; Di Iorio et al , ] to monitor integrated plumes and investigate temporal variability in physical properties such as temperature or flow velocity. This method is based on recovering properties of the medium by measuring fluctuations of the acoustic signal passing through the plume [ Di Iorio et al , ].…”

Section: Measurements Of Advective Heat Output From Seafloor Hydrothementioning

confidence: 99%

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Measuring fluid flow and heat output in seafloor hydrothermal environments

et al. 2015

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We review techniques for measuring fluid flow and advective heat output from seafloor hydrothermal systems and describe new anemometer and turbine flowmeter devices we have designed, built, calibrated, and tested. These devices allow measuring fluid velocity at high‐ and low‐temperature focused and diffuse discharge sites at oceanic spreading centers. The devices perform at ocean floor depths and black smoker temperatures and can be used to measure flow rates ranging over 2 orders of magnitude. Flow velocity is determined from the rotation rate of the rotor blades or paddle assembly. These devices have an open bearing design that eliminates clogging by particles or chemical precipitates as the fluid passes by the rotors. The devices are compact and lightweight enough for deployment from either an occupied or remotely operated submersible. The measured flow rates can be used in conjunction with vent temperature or geochemical measurements to obtain heat outputs or geochemical fluxes from both vent chimneys and diffuse flow regions. The devices have been tested on 30 Alvin dives on the Juan de Fuca Ridge and 3 Jason dives on the East Pacific Rise (EPR). We measured an anomalously low entrainment coefficient (0.064) and report 104 new measurements over a wide range of discharge temperatures (5°–363°C), velocities (2–199 cm/s), and depths (1517–2511 m). These include the first advective heat output measurements at the High Rise vent field and the first direct fluid flow measurement at Middle Valley. Our data suggest that black smoker heat output at the Main Endeavour vent field may have declined since 1994 and that after the 2005–2006 eruption, the high‐temperature advective flow at the EPR 9°50′N field may have become more channelized, predominately discharging through the Bio 9 structure. We also report 16 measurements on 10 Alvin dives and 2 Jason dives with flow meters that predate devices described in this work and were used in the process of their development. This includes the first advective measurements in the Lau Basin and at the EPR 9°39.5′N. We discuss potential error sources and how they may affect the accuracy of measurements by our devices and other devices. In particular, we use the turbulent plume theory to evaluate the effect of entrainment of ambient seawater.

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Section: Measurements Of Advective Heat Output From Seafloor Hydrothementioning

confidence: 99%

“…This method is based on recovering properties of the medium by measuring fluctuations of the acoustic signal passing through the plume [ Di Iorio et al , ]. Using this method, Xu and Di Iorio [] estimated the heat transport of a plume 20 m above an orifice on Dante at the MEF as 62 MW.…”

Section: Measurements Of Advective Heat Output From Seafloor Hydrothementioning

confidence: 99%

Measuring fluid flow and heat output in seafloor hydrothermal environments

et al. 2015

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“…Understanding the relative importance of different scattering mechanisms within a hydrothermal plume is important for the selection of appropriate acoustic models that can transform the existing acoustic techniques to tools of remote sensing of the properties of the suspended particles and temperature/salinity fluctuations within the plume. The dominance of temperature fluctuations within a hydrothermal plume as a scattering mechanism has been previously asserted by Xu and Di Iorio (2011), with strong observational evidence in the case of forward scattering. However, their result is inconclusive for backward scattering due to the lack of contemporaneous acoustic backscatter observation and direct measurements of particle grain size.…”

Section: Introductionmentioning

confidence: 69%

“…Mathematical formulas used to quantify the combined backscatter from individual particles have been developed and applied in many previous studies (Sheng and Hay, 1988;Thorne et al, 1993;Thorne and Meral, 2008;Xu and Di Iorio, 2011). Applying the single scattering approximation and the Rayleigh scattering theory gives the combined backscatter from individual particles as (i.e., backscattering cross-section per unit solid angle per unit volume), and the subscript p refers to individual particles; jA s ðaÞj 2 is the squared backward scattering amplitude of a particle, which is proportional to the sixth power of particle radius (a) in the Rayleigh scattering regime (Palmer, 1996), M is the particle mass concentration in units kg/m 3 , and q s is the mass density of a single particle.…”

Section: A Individual Particlesmentioning

confidence: 99%

The relative effect of particles and turbulence on acoustic scattering from deep sea hydrothermal vent plumes revisited

Jackson

Bemis

2017

The Journal of the Acoustical Society of America

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The relative importance of suspended particles and turbulence as backscattering mechanisms within a hydrothermal plume located on the Endeavour Segment of the Juan de Fuca Ridge is determined by comparing acoustic backscatter measured by the Cabled Observatory Vent Imaging Sonar (COVIS) with model calculations based on in situ samples of particles suspended within the plume. Analysis of plume samples yields estimates of the mass concentration and size distribution of particles, which are used to quantify their contribution to acoustic backscatter. The result shows negligible effects of plume particles on acoustic backscatter within the initial 10-m rise of the plume. This suggests turbulence-induced temperature fluctuations are the dominant backscattering mechanism within lower levels of the plume. Furthermore, inversion of the observed acoustic backscatter for the standard deviation of temperature within the plume yields a reasonable match with the in situ temperature measurements made by a conductivity-temperature-depth instrument. This finding shows that turbulence-induced temperature fluctuations are the dominant backscattering mechanism and demonstrates the potential of using acoustic backscatter as a remote-sensing tool to measure the temperature variability within a hydrothermal plume.

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“…For weak scattering, where the intensity (squared amplitude) variance is less than 0.4 times the mean intensity squared (scintillation index < 0.4), the Born approximation holds and the relationship between the scales of the sound-speed perturbations and the resulting scattered field is defined (e.g., Duda et al 1988;Di Iorio and Farmer 1994) and can be exploited for measurement or data inversion purposes (Xu and Di Iorio 2011). This corresponds to the unsaturated fluctuation regime (Flatté et al 1979;Colosi 2016).…”

Section: Propagation Regimes and Scattering Regimesmentioning

confidence: 99%

Modeling and Forecasting Ocean Acoustic Conditions

Duda¹

2017

j mar res

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Modeling acoustic conditions in an oceanic environment is a multiple-step process. The environmental conditions (features) in the area first must be measured or estimated; relevant features include seabed geometry, seabed composition, and four-dimensionally (4D) variable sound-speed and density variations related to evolving or wave motions. Often the dynamical wave modeling depends on first obtaining correct seabed and mean stratification conditions (for example, nonlinear internal wave modeling). Next, this information must be included in sound propagation modeling. A selection of the many methods and tools available for these tasks are described, with a focus on modeling sounds of 20 to 1000 Hz propagating through water-column features that are time-dependent and variable in three dimensions (i.e., 4D variable). An example of a 3D parabolic equation acoustic calculation shows how variability caused by evolving internal tidal waves affects sound propagation. Different propagation and scattering regimes are discussed, including the theoretically delineated weak scattering and strong scattering regimes, as well as the empirically examined regime found in nonlinear internal waves. The histories and the current state of our oceanographic knowledge (the input to acoustic modeling) and of our ability to effectively model complex acoustic conditions are discussed. Example acoustic simulation applications are also discussed; these are ocean acoustic tomography, coherence prediction, and signal-to-noise ratio prediction. Types of ocean models and acoustic models and how they are interfaced are also examined. These include deterministic, statistical analytic feature models.

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The relative effects of particles and turbulence on acoustic scattering from deep-sea hydrothermal vent plumes

Cited by 15 publications

References 28 publications

Measuring fluid flow and heat output in seafloor hydrothermal environments

Measuring fluid flow and heat output in seafloor hydrothermal environments

The relative effect of particles and turbulence on acoustic scattering from deep sea hydrothermal vent plumes revisited

Modeling and Forecasting Ocean Acoustic Conditions

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