A Canadian and American team worked side-by-side for 45 days in August in the NE Pacific Ocean during the eighth operations and maintenance expedition for OOI’s Regional Cabled Array (RCA). The team used the Canadian remotely operated vehicle (ROV) ROPOS to conduct maintenance operations on RCA’s underwater cabled observatory spanning the Juan de Fuca Plate and at water depths from 80 m to 2900 m. Intense operations included the recovery and reinstallation of 222 instruments and a 2700 m-tall, two-legged Shallow Profiler Mooring. This expedition took place on the global class research ship the R/V Thomas G. Thompson, operated by the University of Washington (UW). Twenty-six students joined the cruise as part of the UW at-sea experiential learning program called VISIONS.
ROPOS is operated by the Canadian Scientific Submersible Facility (CSSF). The vehicle was specially designed for cabled observatory work, bringing in components from the oil and gas field, and a uniquely designed Remotely Operated Cable Laying system (ROCLS) that allows the vehicle to install extension cables extending for several kilometers on the seafloor. Their work culminated in 2014 during an 83-day cruise onboard the R/V Thompson, which resulted in the installation of >15,000 m of extension cables (in total, ~33,000 m of extension cables was installed on the seafloor), >140 instruments, and platforms on the six-state of-the art moorings with instrumented profiling vehicles. They also installed 18 junction boxes at the key experimental sites using their underbelly latching system that allows the vehicle to directly secure loads up to 4,000 lbs beneath the vehicle. This latching system was adopted by the Deep Submergence Facility ROV Jason, which has conducted multiple RCA maintenance cruises.
During this latest expedition, ROPOS conducted 60 dives over 33 at-sea days. Keith Tamburri led seven members of the ROPOS team, who worked 12 hours on, 12 hours off for 45 days. Operations are more similar to industry with as little time on deck as possible for the ROV, typically about three hrs before ROPOS reentered the water. Team work is exemplified during ROPOS operations where two pilots each operate a manipulator to conduct complex operations. The ROPOS team was joined in the dive control laboratory by varying members of the RCA’s team, who directed ROPOS activities on the seafloor and throughout the water column, and the VISIONS’22 students who stood 4 hour watches. (A list of ROPOS and RCA team members can be found here).
During this 8th RCA recovery and deployment expedition, the R/V Thompson traveled to all of the RCA sites. ROPOS recovered and redeployed a diverse array of instruments and four small seafloor substations that provide power and communications to instruments on the seafloor and to the instrumented Deep and Shallow profiler moorings. The ROV also was used to install a 500 m long extension cable that allowed bringing the Southern Hydrate Ridge live again. ROPOS also recovered equipment and samples for externally funded principal investigators, including several novel instruments developed by scientists in the US and Germany. ROPOS tasks were many and varied. The vehicle emplaced packages up to 3200 lbs in weight and the pilots skillfully used the manipulators to do everything from scrubbing biofouling off cables to unplugging and plugging in instruments to the seafloor cable
In addition to RCA operations, ROPOS was used to help advance scientific investigations involving instruments added onto the RCA cabled network. For example, as part of an Early Career award to for Dr. Rika Anderson at Carleton College, ROPOS conducted sampling dives using a Universal Fluid Obtainer on the ROPOS porch to sample fluids for follow-on analyses of microbes and viruses. Through another NSF award to Dr. Wilcock and his UW colleague Dana Manalang, ROPOS installed a first of its kind acoustic network on the western and eastern rim of Axial Seamount and within its caldera to examine deformation within the caldera. A suite of CTD instruments were also turned within the caldera to test the hypothesis that brines are emitted from the subsurface associated with submarine eruptions as part of and NSF award to Dr. William Chadwick at the Oregon State University. Lastly, ROPOS inspected a Quantification sonar and recovered an Overview Sonar on Southern Hydrate Ridge as part of a project funded by the German Federal Ministry of Education and Research to MARUM at the University of Bremen, led by investigators Gerhard Bohrmann and Yann Macron. In addition, their 4K high-definition camera was cleaned and a CTD turned. The sonar and camera instruments are another example of an international collaboration.
“Our ROPOS team really enjoys working with the team from the University of Washington, School of Oceanography and Applied Physics Laboratory, who are responsible for the RCA. They are a professional, well-organized, efficient, friendly, and mutually respectful group, which makes these long missions at sea productive, efficient, and successful,” said Keith Shepherd, General Manager, Canadian Scientific Submersible Facility. “And for this cruise, in particular, it was a real pleasure working along with UW undergraduates onboard as part of UW’s at-sea experiential program VISIONS. The students brought a curiosity, enthusiasm, and energy that were always welcome during the long hours in the dive control van.”
Added Kelley, “It really takes a tremendous amount of time, effort, and teamwork to pull off an expedition of this length and complexity. We are grateful to have had the opportunity to work again with our Canadian colleagues. It was an excellent international collaboration to help maintain and expand the capabilities of the RCA. “ Because of the complex nature of the undersea work required to keep the RCA operational, few facilities are trained and equipped to execute such operations.