The PI's request funding to develop a pair of camera systems that are specifically designed to use OPV (VentCam) and DFV (Diffuse Effluent Measurement System (DEMS)) to measure the velocities of focused and diffuse hydrothermal flows in these environments. The VentCam system will use OPV to perform time-series velocity measurements on black smoker fluids using a high-speed, high resolution camera with automatic panning that maintains the flow in the field-of-view during sulfide chimney growth. The DEMS will measure diffuse fluid velocities using a camera attached at a fixed distance from a background specially designed for DFV calculations. Simultaneous temperature measurements by thermocouples placed in high-temperature vent orifices as well as low-temperature loggers coupled to the DEMS will help constrain the partitioning of diffuse and focused heat fluxes and the amount of crustal cooling attributable to axial venting. Measuring the rates at which hydrothermal fluids exit the crust, and how those rates change over time, is critical for understanding these systems and the complex linkages between their component parts. Such measurements can provide information about the structure of permeability in the subseafloor, the geometry of hydrothermal circulation patterns, fluxes of heat and chemicals exchanged with the overlying ocean, and the potential productivity of subseafloor ecosystems.
Broader Impacts:
Knowledge gained using these tools will improve our understanding of hydrothermal fluid fluxes and their contribution to a variety of chemical, biological and physical processes. The project will support two early career scientists who were responsible for developing the optical methods to be used by these imaging systems. The Mentoring plan for the post-doc is well described and likely to result in successful development of the researcher during the projects lifetime. When developed and tested, the instruments have potential for longer-term time series if connected to regional seafloor cabled observatories like the Regional Serial Nodes observatory under development on the Juan de Fuca Ridge.
Hydrothermal venting influences ocean chemistry , the thermal and chemical structure of the oceanic crust, the style of accretion at mid-ocean ridges , and the evolution of unique and diverse chemosynthetic ecosystems. Measuring the rates at which hydrothermal fluids exit the crust, and how those rates change over time, is fundamental to understanding these processes, but existing instruments for measuring fluid velocities, although innovative and informative, can clog or perturb flow and bias estimates. This proposal aimed to create a new pair of non-invasive instruments that accurately measure the velocity of hydrothermal fluids. Our camera system is designed specifically to take advantage of a recently developed optical method, Diffuse Flow Velocimetry (DFV), which measures fluid velocities using image-correlation techniques. DFV calculates fluid velocities by analyzing video imagery of the flows, so this method is non-invasive (i.e. it does not alter the flow under inspection). DFV can provide time-series measurements of both diffuse and focused hydrothermal flow over long periods of time. The system we developed (Diffuse Effluent Measurement System (DEMS)) is configured to measure the mass and heat flux from diffuse hydrothermal vents. The system is capable of using battery power to perform time-series measurements at specific, well-established diffuse venting locations along the mid-ocean ridge axis. In addition, to increase the spatial coverage of measurements of widespread diffuse flow, the DEMS background board can be attached to an ROV manipulator arm and used for capturing imagery from calibrated camera systems. In this configuration, the DEMS is estimated to be able to perform approximately 25 discrete measurements within ~2.5 hours (depending upon the number of ROV displacements), a reasonable timescale relative to the tidal cycle. This configuration was tested in September, 2014 at the Kick’em Jenny Volcano. The DEMS can now provide the broad oceanographic community a new tool to examine the connections between biological, mechanical, and chemical processes and the fluxes of diffuse hydrothermal fluids.
