Dave Butterfield checking fluid connections to the methane spectrometer (large black pressure case) mounted at the back of ROV Jason’s tool sled. Other equipment used on this dive include the auxiliary pump at left, 3 titanium gas-tight sampler with colored T-handles, a suction sampler (large orange hose) and the Hydrothermal Fluid Sampler intake nozzle at far right. Photo Credit: Andrew Fahrland (OKSI)
NOAA PMEL, University of Washington and OptoKnowledge Systems, Inc. (OKSI) successfully conducted the first deep water test of a new methane analyzer to measure the concentration and carbon isotope ratio of methane near Axial Seamount. This new instrument can collect data that will improve scientists’ understanding of carbon cycling, greenhouse gasses, and sub-seafloor chemosynthetic reactions.
After 3 years of testing and development, the analyzer was mounted on the remotely operated vehicle Jason and coupled to PMEL’s hydrothermal fluid and particle sampler (HFS) during a recent cruise on the Research Vessel Thompson. The methane analyzer combines a novel laser absorption spectroscopy gas sensor with a membrane-free approach to water sampling. While the research cruise had to be cut short, the team successfully was able to collect valuable data and coordinate samples for cross-calibration during one ROV dive.
While collecting data with the methane analyzer, researchers simultaneously sampled the same fluid in gas-tight samplers attached to the fluid manifold and in custom samplers that are part of the HFS. Methane concentrations analyzed onboard the R/V Thompson by gas chromatography on fluid samples from HFS piston and bag samplers agree well with the in-situ methane concentrations determined by the analyzer.
Ultimately, the instrument worked well on the ROV and it is expected that the methane spectrometer will have many useful applications.
Learn more about this technology development and methane work on PMEL’s Earth Ocean Interactions research page.
Instrument Development:
The methane analyzer was developed by OKSI with initial funding from the NOAA Small Business Innovation Research (SBIR) Program. The SBIR Program, also known as America’s Seed Fund, awards seed funding to U.S. small businesses to support high-risk, high-reward research and development of new technologies. In 2016, OKSI received a NOAA SBIR Phase I award to develop an instrument that could analyze underwater gasses, specifically methane and its isotopes. The company was awarded follow-on Phase II funding in 2017.
The effort has since transformed into a Phase III collaboration with PMEL. OKSI and NOAA PMEL were funded in 2019 through a National Ocean Partnership Program (NOPP) grant with NOAA Ocean Exploration support to continue development of the methane spectrometer and deploy it in deep water. In 2021, PMEL and OKSI successfully completed shallow-water methane concentration measurements in Puget Sound. The Puget Sound test showed that the instrument can take measurements of methane concentration in-situ and report those measurements in real-time to an operator on board a ship with an update rate approximately every 6 minutes.
More About the Sensor:
For the new spectrometer instrument, it is important to verify that the in-situ measurements agree with established discrete sampling and analysis for methane concentration and carbon isotope ratio. The PMEL hydrothermal fluid sampler, first developed in 1998, will deliver warm hydrothermal fluids from diffuse vents with elevated methane concentrations to the methane spectrometer and simultaneously take coordinated discrete samples for laboratory analysis of concentration and carbon isotope ratio to cross-calibrate the in-situ measurements from the methane sampler. Tamara Baumberger is collecting samples in specialized gas-tight samplers for carbon isotope and methane concentration analysis.