The PI's request funding 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). The backbone cable for this RCO was installed in 2007 and the nodes and junction boxes are scheduled for installation in 2009. The proposed 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 proposed new instrumentation, the Cabled Observatory 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. 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 and angular translation system. 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.
Broader Impacts:
This work should enable a real-time window to seafloor hydrothermal flow and its interaction with oceanic and geological processes. The great public awareness and educational impacts this installation could have for the general public and K-12 through college education/inspiration are obvious and should be encouraged. There may be some thesis benefits for engineering graduate students, as well.
Hot springs, discharging from the seafloor in the deep ocean, are important Earth processes, because they transfer heat, inorganic chemicals, and organic matter from beneath the seafloor into the ocean in amounts that cool the Earth, influence the composition of the ocean, and support chemosynthetic ecosystems of animals and microbes new to science. Photos and videos use light to illuminate the seafloor hot springs and to make spectacular images of individual black smoker type vents discharging plumes of particles that look like smoke into the ocean. Figure 1 shows a photo of black smoker with the plume rising to about the height of a person. In contrast to photos and videos which make pretty pictures, sound waves can actually probe the entire hot springs and enable quantitative measurements of their discharge and impact on the ocean. We (scientists from Rutgers University partnered with scientists and engineers of the Applied Physics Laboratory of the University of Washington) have developed a sonar system in order to use sound to probe the discharge from the seafloor vents. The sonar images the plumes in 3D and the surrounding seafloor seeps in 2D to measure flow rates and volume fluxes as quantitative measures of their impact on the ocean. We connected our Cabled Observatory Vent Imaging Sonar (COVIS) to a seafloor observatory called NEPTUNE Canada. The observatory is connected by a fiber optic-electrical cable like a submarine telephone cable from the hot springs on a submerged volcanic mountain range nearly 200 miles offshore the northwest coast of Canada in the Pacific Ocean to a shore station. The sonar images are transmitted from the shore station to our laboratories where the images are viewed and analyzed in near real time. Figure 2 shows a typical false-color image from our data with the plume internal structure in shades of red to purple and the intensity of the seeps in shades of orange to gray draped on the seafloor topography. We derive information from the sonar images on how the discharge from the remote seafloor hot springs is cooling the Earth, influencing the chemistry of the ocean, and supporting life in the ocean. In turn, we see how the discharge from the hot springs is influenced by tides, storms, earthquakes and volcanic eruptions on the seafloor. This information enables us to develop an understanding of the role of seafloor hot springs in creating living (biological) and non-living (mineral) resources and in influencing the environment of the deep ocean; such understanding enhances our ability as a society to protect the environment which is part of the balanced working of our planet and derive new natural resources.
