Acoustic Imaging and Computer Visualization

of

Seafloor Hydrothermal Flow Regimes

Peter A. Rona Darrell R. Jackson
Institute of Marine and Coastal Sciences Applied Physics Laboratory
Rutgers University University of Washington

rona@imcs.rutgers.edu

drj@apl.washington.edu


Contents

Project Scope

We use acoustics in coordination with visualization and quantification methods to image and measure smoker-type plumes in 3D and to map diffuse flow in 2D The plumes originate as clear, hot (c. 150o to 400oC) solutions that vent from mineralized chimneys, precipitate dissolved metals as they mix with ambient seawater, and buoyantly rise up to hundreds of meters. The seepage discharges as clear diffuse flow at lower temperatures (<150oC) from networks of fractures at the rock/water interface and may be entrained into plumes or disperse in discrete layers. These flow regimes are being intensively studied for their role as agents of transfer of heat, chemicals and microbes from the lithosphere into the ocean that globally influence seawater composition, cool the Earth, contribute to climate change, concentrate metallic mineral deposits, and support chemosynthetic ecosystems.

Focused Flow: We are measuring two aspects of high temperature flow from black smokers: the distribution of particulate matter is measured using volume backscattering and upward flow velocities are estimated using a incoherent Doppler technique. Plumes are imaged in 3-D by volume backscattering from suspended particulate matter.  A variety of visualization methods are applied to quantify the particle distribution in order to make comparisons with numerical and analytical model predictions.

Diffuse Flow: Diffuse flow is imaged by distortion of an acoustic pulse by sound speed variations related to random temperature fluctuations as the sound pulse travels through and is reflected from the seafloor back through a lens of warm water.

Past Study Areas

  1. Clam Acres area of the Southwest Vent field, 21oN EPR.
  2. Monolith Vent, Cleft Segment, Juan de Fuca Ridge.
Present Study Areas

1. Main Endeavor Vent Field, Endeavor Segment, Juan de Fuca Ridge

            Our work here was part of the RIDGE Endeavour Observatory program. 

Study Participants

 

Dr. Peter A. Rona

rona@imcs.rutgers.edu

Dr. Darrell R. Jackson

drj@apl.washington.edu

Dr. Karen G. Bemis

bemis@rci.rutgers.edu

Dr. Christopher D. Jones

cjones@apl.washington.edu

Dr. Deborah Silver

silver@caip.rutgers.edu

Dr. David Palmer

palmer@aoml.noaa.gov

Dr. Kyohiko Mitsuzawa

mitsuzawak@jamstec.go.jp

Ravi Gudlavalletti

gudlaval@caip.rutgers.edu

Rajesh Chandrasekaran

crajesh@caip.rutgers.edu

Lian Jiang

lianjian@caip.rutgers.edu

Recent Cruise

VIP (Vent Imaging Pacific) 2000 Cruise Summary

            The objective of the VIP 2000 cruise (R/V Thompson cruise 114 with ROV Jason; 21-31 July 2000) was to acoustically image and quantify hydrothermal flow regimes (diffuse flow and black smoker plumes) at representative sites in the Main Endeavour Vent Field. The acoustic measurements were made in coordination with in-situ monitoring and measuring of these flow regimes by other cruises as part of the NSF RIDGE Program Endeavour Observatory Experiments.

We employed the Simrad SM 2000 sonar system, operating at 200 kHz, mounted on ROV Jason and modified by the addition of a mechanical rotator and related software to scan plumes. The acoustic imaging work was accomplished on two dives of ROV Jason, one dive of short duration (Dive JAS-282; 07/23/00; 17 hours) and one of long duration (Dive JAS-283; 07/24-28/00; 112 hours, a standing record for the duration of a Jason deployment). A third dive (Dive JAS-285) was aborted to change a malfunctioning temperature sensor. The fourth and final dive (JAS-285) was devoted to in-situ measurements of temperature and flow rate at selected black smoker vents and areas of diffuse flow that were imaged, and moderate sampling of biota on active chimneys (for a participating Canadian biologist).


            We performed 5 types of acoustic experiments on hydrothermal flow regimes in the Main Endeavour Field (Rona et al., 2000), as follows:


1)   Panoramic imaging: Sonar imagery at the Peanut-Puffer-Bastille group, Salut (Fig. 2), S & M and Grotto sites shows seafloor features, plumes (based on acoustic backscatter), and diffuse flow (based on acoustic scintillation thermometry). The images reveal differences between the 4 vent clusters in intensity of venting and partitioning between black smoker plumes and diffuse flow.

2)     Time series of a panoramic image: The time series (5 images per hour during 24 hour period at Grotto vent site) shows the effect of a mixed semi-diurnal tide on intensely venting plumes and diffuse flow (Fig. 3); Bemis et al., 2000; Rona et al., 2001). In-situ measurements of temperature and flow rates were made at black smoker vents and in diffuse flow.

3)     Diffuse flow: Acoustic scintillation tomography (AST) mapping of diffuse flow was conducted to test operating modes: stationary on the seafloor, hovering (Fig. 5; Rona et al., 1997; Jones et al., 2000), and moving. The hovering mode was adapted for mapping areas of diffuse flow.

4)      Flow rates: The incoherent Doppler method is being developed and applied to measure flow rates in the buoyant plumes of black smokers (Fig. 6; Jackson et al., 2000).

5)     Shadowing and scattering effects: Absorption loss by acoustic backscatter in a plume was measured to determine the shadowing effect of suspended particulate matter on acoustic transmission.

6)     Bathymetry and water column: In addition to the acoustic experiments, we ran several high-resolution bathymetric lines to fill gaps in a bathymetric survey of the Main Endeavour Vent Field initiated on a prior leg and recorded two CTD-transmissometer profiles in the study area.

Link to Cruise Report (pdf format, 33.6 Mb)

Visualization Methods

Visualization has been carried out at Laboratory of Visiometrics and Modeling, Computer Aids for Industrial Productivity (CAIP) Center, Rutgers University.


For detailed visualization methods and results, 

Publications

Bemis, K.G., D. Silver, P.A. Rona, and C. Feng, Case Study: a methodology for plume visualization with applications to real-time acquisition and navigation, IEEE Visualization 2000, IEEE, 481-494, 2000.

 

Bemis, K.G., P.A. Rona, D. Jackson, C. Jones, D. Silver, K. Mitsuzawa, A comparison of black smoker hydrothermal plume behavior at Monolith Vent and at Clam Acres vent field: dependence on source configuration, Marine Geophys. Res., in press

 

Feng, C., D. Silver, K.G. Bemis, P. Rona, Acoustic imaging manual: object segmentation and feature quantification, Technical Report CAIP-TR-242, Center for Advanced Information Processing, Rutgers University, 55 p., 1999.

 

Jackson, D.R., C.D. Jones, P.A. Rona and K.G. Bemis, Doppler measurement of black smoker flow velocity, EOS, Trans. Am. Geophys Un., 81(48), F641, 2000 .

 

Jones, C.D., D.R. Jackson, P.A. Rona, and K.G. Bemis, Acoustic observation of hydrothermal flows, J. Acoust. Soc. Am, 108:5:Pt. 2:2544-2545, 2000.

 

Palmer, D.R., P.A. Rona and M.J. Mottl, The acoustics of “black smoker” hydrothermal  plumes, J. Acoust. Soc, Am 80. 888-898, 1986.

 

Rona,. P., K.G. Bemis, D. Kenchammani-Hosekote, and D. Silver, Acoustic imaging and visualization of plumes discharging from black smoker vents on the deep seafloor, IEEE Visualization ’98, 475-478, 1998.

 

Rona, P.A., D. R. Jackson, T. Wen, C. Jones, K. Mitsuzawa, K.G. Bemis, and J.G. Dworski, Acoustic mapping of diffuse flow at a seafloor hydrothermal site: Monolith Vent, Juan de Fuca Ridge, Geophys. Res. Letters, 24: 2351-2354, 1997.

 

Rona, P. A., Palmer, D. R., Jones, C., Chayes, D. A., Czarnecki, M., Carey, E. W., and Guerrero, J. C., Acoustic imaging of hydrothermal plumes, East Pacific Rise, 21N, 109W, Geophysical Research Letters, 18, 2233-2236, 1991.

Background

1. Why study Hydothermal Plumes?
    E. Baker at NOAA/PMEL.
    Click here for detailed information.
2. Diffuse Venting and its Relationship to Focused Sources
    J. W. Lavelle at NOAA/PMEL.
    Click here for detailed information.

Acknowledgements

We acknowledge outstanding support of our acoustic imaging cruises received from the Deep Submergence Group and the ROV Jason team of the Woods Hole Oceanographic Institution; from the Marine Office, officers and crew of the R/V T.G. Thomson of the University of Washington to the Endeavour Observatory (VIP/Vent Imaging Pacific 2000 cruise); and from U.S. Navy Deep Submergence Group One to the East Pacific Rise and the southern Juan de Fuca Ridge. We thank Norman Zabusky and Deborah Silver, directors of the Laboratory for Visiometrics and Modeling at Rutgers University, for their guidance and generosity in granting us access to their expertise, students and facilities. This research was supported by NSF RIDGE Program Grant OCE 98-18841 to PAR and DRJ and by the NOAA West Coast and Polar National Undersea Research Program.



Last update: 4/25/2002. Please send any comments to bemis@rci.rutgers.edu.