A group of Ocean Observatories Initiative (OOI) leaders visited OOI facilities at Oregon State University and the University of Washington last week to get a first-hand look at operations of the Coastal Endurance Array and Regional Cabled Array, respectively. National Science Foundation Program Director George Voulgaris, OOI Principal Investigator Jim Edson and Senior Program Manager Paul Matthias spent five days on the road meeting with their OOI west coast colleagues. The trip was designed to give recently appointed Voulgaris an opportunity to inspect the infrastructure and meet team members who keep the Coastal Endurance and Regional Cabled Arrays operational and reporting back data around the clock. Edson and Matthias seized the opportunity to meet in person with colleagues who they routinely see on the screen.
The following provides a glimpse of some of the activities that occurred during the trip:[media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230207_140014.jpg" link="#"]Grant Dunn, Mechanical Engineer with the Electronic & Photonic Systems Department at UW-APL (left) describes the level-wind system on the RCA profiler mooring to Dr. George Voulgaris during a tour of the RCA laboratory facilities at the University of Washington as RCA Project Manager Brian Ittig looks on. Credit: Paul K. Matthias © WHOI.[/media-caption] [media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230207_144911.jpg" link="#"]Regional Cabled Array Principal Investigator Deborah Kelley (left) and OOI Senior Program Manager Paul Matthias take a selfie to commemorate their in-person visit during a tour of the RCA facilities at the University of Washington. Credit: Paul K. Matthias © WHOI.[/media-caption] [media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230207_141656.jpg" link="#"]NSF Program Director George Voulgaris (from left), OOI Principal Investigator Jim Edson look on as Regional Cabled Array technicians Grant Dunn, Mechanical Engineer with the Electronic & Photonic Systems Department at UW-APL, and RCA Chief Engineer Chuck McGuire explain the engineering associated with the RCA profiler mooring during a tour of RCA’s facilities at the University of Washington. Credit: Paul K. Matthias © WHOI.[/media-caption] [media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230209_123758.jpg" link="#"]NSF Program Director George Voulgaris (left) asks OSU technician Jonathan Whitefield questions about glider operations that provide critical water column data around the moorings of the Coastal Endurance Array. Credit: Paul K. Matthias © WHOI.[/media-caption] [media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230207_112718.jpg" link="#"]NSF Program Director George Voulgaris (foreground) and RCA Chief Engineer Chuck McGuire discuss the RCA data monitoring systems as OOI PI Jim Edson points to real-time data on the screen being relayed by instrumentation on the Regional Cabled Array. Credit: Paul K. Matthias © WHOI.[/media-caption] [media-caption path="https://oceanobservatories.org/wp-content/uploads/2023/02/20230209_130353.jpg" link="#"]NSF Program Director George Voulgaris (left) gets a hands-on look at the multiple instruments contained on multi-function node that will sit on the bottom of the ocean floor for six months collecting data for the Coastal Endurance Array. Coastal Endurance Array Principal Investigator Ed Dever (middle) and Project Manager Jonathan Fram the functionality of each instrument during the visit to Oregon State University. Credit: Paul K. Matthias © WHOI.[/media-caption]
OOI’s Coastal Endurance Array Team is making great strides in ensuring the accuracy of glider dissolved oxygen measurements and making these data readily available to researchers. The team has compared glider oxygen data with independent transects and climatologies compiled by west coast colleagues. They are increasing the number of in situ comparisons of glider oxygen data with bottle samples taken in proximity to the gliders. They have built a benchtop system to do two-point calibrations for oxygen sensors to help ensure their accuracy when the gliders are in the water. And, working with OOI colleagues at WHOI, the team is helping to design and test improved sensor mounts to perform in situ air calibrations of glider oxygen measurements.
“A couple of years ago, Endurance Glider Lead Stuart Pearce developed code to put all of the oxygen data collected by our glider fleet into the DAC, the national central database for glider data,” said Ed Dever, Principal Investigator of the Coastal Endurance Array and Professor at Oregon State University. “Prior to doing this, Stuart examined the data and metadata for any gross errors and issues. That was the first of many steps we have taken to ensure OOI oxygen data are reliable and available so they can be trusted and used by researchers. Our effort is paying off. The glider data available on the DAC are identical to that now available on OOI’s Data Explorer. Endurance glider lines off Newport, OR and Grays Harbor, WA will be the backbone for the northern Californian Current part of the nascent Boundary Ocean Observing Network. The OOI glider lines map seasonal development of hypoxic areas off Oregon and Washington from the coast to the edge of the continental shelf.”
[media-caption path="/wp-content/uploads/2022/11/glider.png" link="#"]More than 137 glider missions have occurred along the Newport and Grays Harbor lines since 2014. Credit: Coastal Endurance Array at OSU.[/media-caption]
Enough oxygen data has been collected and shared in the northeast Pacific that is now possible to make high resolution regional climatologies of temperature, salinity and oxygen. Risien et al. (2022) compiled ~20 years of data taken by Jennifer Fisher (NOAA) and many others, to develop analysis ready transects of water property data off Newport, Oregon. These datasets include both climatologies and individual interpolated, quality-controlled, transect data. The Endurance Team compared glider dissolved oxygen with shipboard CTD samples collected by Fisher along the Newport transect in July 2021. Oxygen measurements from the gliders and CTDs samples compared well and provided confidence that glider and shipboard transects can map hypoxic conditions at comparable resolution and accuracy. Added Dever, “We were able to do a side-by-side comparison of the temperature, salinity, and oxygen data collected by the gliders over our Newport hydrographic line with the CTD data sampled by the Fisher’s team using the R/V Elakha. The comparison was quite good and served to validate the quality of the glider data that are an integral part of the Endurance Array.”
A couple years ago, team member Jonathan Whitefield worked with Scripps Institution for Oceanography to build an oxygen Winkler titration rig so the team can titrate its own oxygen samples. The system can be used both in the lab and onboard to validate glider and moored oxygen data. The titration rig has been used to increase the number bottle samples taken during glider deployments and recoveries and to reduce the time between sample acquisition and analysis.
Building on this, Whitefield and others recently assembled in-house two-point calibration baths for pre- and post deployment of oxygen data collected by gliders and moorings. Calibrations are performed at anoxic and near-saturated conditions. The two-point calibration system is based on a similar one used at Scripps Institution for Oceanography (López-García, P., et al., 2022). A sodium sulfite solution is injected into bottle samples to get the low endpoint oxygen calibration point. The high endpoint oxygen calibration point is achieved using a stirred bath at 10°C to get to near saturation. The high endpoint oxygen is measured with replicate Winkler titrations. The calibration baths better ensure accuracy by making it possible to perform routine in-house checks of vendor calibrations on glider and moored sensors as well as identify calibration drift after deployment.
Oxygen data are reviewed weekly by operators and annotated. Real-time automated quality control using QARTOD tests is in development. In-situ air calibration tests of oxygen optodes are planned for spring 2023. At the suggestion of outside investigators, OOI’s Coastal and Global Scale Node team at Woods Hole Oceanographic Institution modified Slocum glider optode mounts to allow in-situ air calibrations of dissolved oxygen on the Irminger Sea and Pioneer Arrays. The mount, however, affected the flow around gliders with radome fins and caused navigation problems. Modeling done at WHOI showed these problems may be due to vortices of the optode on the starboard side of the fin. The Endurance gliders will test a new mount placement during its upcoming bi-annual operations and maintenance cruise in March of 2023.
“We’re part of the community of practice for glider oxygen calibration and validation,” said Dever. “We engage with colleagues, adopt standard practices and widely share data. This community of users will help all of us get a better handle on ongoing changes in our ocean regions.”
Risien et al. (2022) Spatially gridded cross-shelf hydrographic sections and monthly climatologies from shipboard survey data collected along the Newport Hydrographic Line, 1997–2021, https://doi.org/10.1016/j.dib.2022.107922
López-García, et al. (2022) Ocean Gliders Oxygen SOP, Version 1.0.0. Ocean Gliders, 55pp. DOI: http://dx.doi.org/10.25607/OBP-1756. (GitHub Repository, Ocean Gliders Oxygen SOP.