Acoustic Imaging &
Computer Visualization of Seafloor
Hydrothermal Flow


                  Cabled Observatory Vent Imaging Sonar System (COVIS)

Acoustic Instrumentation for Imaging and Quantifying Hydrothermal Flow in NEPTUNE Canada Regional Cabled Observatory at Main Endeavour Field, JdFR. Russ Light (PI), Vern Miller and Darrell Jackson, Applied Physics Lab, University of Washington; Peter Rona (PI) and Karen Bemis, Rutgers University (NSF Award ID 0825088; 01 November 2008 to 31 October 2010) Collaborative Research.

This is an engineering proposal to develop and connect sonar instrumentation to monitor hydrothermal flow at the NEPTUNE Canada Regional Cabled Observatory (RCO) in the Main Endeavour Field (MEF) on the Juan de Fuca Ridge (JdFR) offshore British Columbia as part of the Ocean Observatories Initiative (OOI).

                                                                                                                                                                Image courtesy NEPTUNE Canada.


                                                                                                                                           Map from Delaney et al., 1992.

The backbone cable for this RCO was installed in 2007 and the nodes and junction boxes are scheduled for installation in 2008. Our instrumentation will acoustically image time series of the changing 3D geometry, flow rate and volume flux of buoyant plumes discharging from vents and areal distribution of diffuse flow from the surrounding seafloor. Connection to NEPTUNE Canada will provide the power and bandwidth to extend our present technically proven capability of imaging from days/weeks (ROV or battery power) to months/years. This temporal extension will enable monitoring of fluxes of hydrothermal flow and detecting linkages with external forcing processes from tidal cycles to geologic events (earthquakes, volcanic activity).

                                                       The Sonar position realtive to the Hydrothermal Plume.

The proposed new instrumentation, the Cabled Observatory Vent Imaging sonar System(COVIS), is designed as an ideal instrument for the power and data bandwidth afforded by the cabled observatory and will adapt to NEPTUNE Canada Stage I mechanical, electrical, and software functional requirements (NEPTUNE Canada letter appended). A state-of-the-art commercial off-the-shelf sonar (400 kHz) will be acquired and integrated onto a custom benthic tripod lander with a central tower (5 m high) and angular translation system (3 degrees of freedom). All necessary electrical and mechanical systems will be implemented to allow placement of the COVIS by ROV and direct connection to a NEPTUNE instrumentation node. The 3-axis angular translation system will allow operators to precisely position the multi-beam sonar head into observing positions for both plume and diffuse flow measurements, will be adaptable to changes of the flow orientations, will be capable of autonomous response to significant geophysical events detected by other NEPTUNE Canada instrumentation via shore based control software, and will have scope to be moved within the vent field. The sonar instrumentation package is designed to adapt to a seafloor site at a vent cluster in the MEF within range of the node/junction box to be emplaced by NEPTUNE Canada (water depth ~2200m), and our acoustic imaging will be coordinated with in situ measurements at the vents(temperature, chemistry, biology) by other investigators to maximize the scientific return.
We will provide a near real-time user-friendly data product for the community (3D images of buoyant plumes), will develop automated signal processing for the large data acquisition rates anticipated, and will apply our proven methods to measure 3D geometry, flow rate and volume flux of buoyant plumes and area of diffuse flow.


Broader Impacts.
The proposed engineering and connection to the NEPTUNE Canada RCO is transformational:
(1) Extension of the capability to monitor hydrothermal flow way beyond present time limits(weeks) enables the measurement of long term changes in fluxes and elucidates linkages between flow and external forcing by oceanic and geologic processes(years). 
(2) Our innovativesonar platform and triaxial translation system has broad application to other types of instrumentation for cabled observatories 
(3) Opening a real-time window to seafloor hydrothermal flow and its interaction with oceanic and geologic process will contribute to K-12, undergraduate, and graduate research projects, and public outreach through established programs. 
(4) Our work has the potential to score an early success for the NSF Ocean Observatories Initiative (OOI) using the established NEPTUNE Canada Regional Cabled Observatory (RCO) years in advance of the U.S. Regional Scale Nodes.




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