The PI has requested funding to develop and test a seafloor camera system that can measure fluid flow through black smoker hydrothermal vents using video image analysis. Fluid flow through black smoker vents plays a significant role in the exchange of heat and chemicals between the oceanic crust and the ocean. This flow delivers energy to a diverse subseafloor ecosystem and serves to link tectonic and magmatic processes to chemical and biological processes. Measurements of fluid flow in these systems are essential for measuring fluxes and understanding complex systematic linkages. Despite the importance of measuring fluid flow rates, there is currently no instrument capable of obtaining long term flow measurements in black smoker vents. High temperatures, low pH, and mineral precipitation make invasive techniques infeasible. To address this problem, The PI proposes to develop a non-invasive image-based instrument to obtain flow rates in black smoker vents. This camera system will employ a new technique for measuring black smoker flow, called Optical Plume Velocimetry (OPV), which has been developed in the laboratory and has been shown to work well on simulated black smoker flows.
Broader Impacts
This study will develop an instrument that will increase our ability to understand the hydrology of marine hydrothermal systems and a variety of related processes, including the interactions between geomechanical processes and other processes such as heat and chemical transport and biological productivity. The development and field test of this technology will open up a wide range of possible experiments at many vent fields on the mid-ocean ridge. This work will also support the work of a young scientist. Crone has a strong record of public outreach through the media, and communicating his results to scientific and general audiences.
The VentCam is a seafloor instrument being developed to measure flow rates in mid-ocean ridge hydrothermal vents using video image analysis. Measuring flow in these systems is extremely difficult, and few measurements have ever been made. No long-term flow rate records have been collected from any high-temperature vent, primarily because fluids are typically very hot, highly acidic, and saturated with minerals that precipitate upon mixing with seawater—conditions which can clog or otherwise harm "invasive" flow meters. Despite the difficulty of measuring such flows, these observations will be critical for developing well-calibrated models of heat transport and crustal formation at mid-ocean ridges. They are required for quantifying chemical fluxes between the deep ocean and the crust, mapping patterns of hydrothermal flow in the lithosphere, and understanding the dynamic geological and biological processes that occur below the seafloor. Measurements of flow will provide insights into the linkages connecting these myriad system components, and will help elucidate processes that support and sustain the diverse ecosystems that thrive in these environments. The current prototype VentCam represents an important step forward in terms of understanding the hydrology of these systems and the deep biosphere sustained by hydrothermal flow in the Earth’s crust. During this project we designed and built a prototype VentCam system and deployed it at two hydrothermal fields in the eastern Pacific Ocean. The system consisted of a large tripod base that could be manipulated by an underwater robot or submersible, a high-speed camera in a pressure resistant housing, batteries, lighting, a data acquisition system, and a set of sighting lasers to assist in positioning and alignment. We deployed this system at the East Pacific Rise in 2009, and at Axial Volcano in 2010. The deployments were very successful, and provided essential information necessary to continue the development of this platform, including the power, lighting, and optical requirements of the system. The deployments also provided the opportunity to evaluate the performance of the system when used with different submersible platforms , as well as test a number of the data acquisition algorithms, including the light detection and balancing routine, and the lossless video compression scheme. In 2010, the optical flow algorithm, OPV, which the VentCam will incorporate, was used by the PI on this grant to estimate the rate that oil was flowing from the Deepwater Horizon blowout in the Gulf of Mexico. This method was developed by the PI specifically for measuring flow rates in turbulent buoyant jets using image analysis. Later government estimates of the flow rates supported the accuracy of OPV. Combined with OPV, the VentCam prototype is now well-positioned to be developed into an instrument suitable for long-term deployment or for connection to the OOI cabled observatory system.
