Although our visit to Axial Seamount on this leg was brief, we accomplished much in the roughly 36 hours we spent onsite. That included OOI work as well as two unplanned but 100% successful inter-institution cooperative rescue operations for a stranded AUV and a drifting piece of equipment!
Our first stop was at the Shallow Profiler Mooring at the base of Axial Seamount, where we swapped out the two “saddle bags” that house the scientific instruments on the mooring platform. This annual endeavor was more complex this year because the Shallow Profiler Pod has been stuck 160 meters from its normal docking location due to a winch issue, which had it sitting about 40 meters below the surface. Rather than being able to recover the pod in its dock at 200 meters water depth, Jason was equipped with a hydraulic bandsaw (very exciting!) to cut the cable connecting the pod to the Shallow Profiler Mooring. They fired up the saw and released the pod to the surface, where the R/V Thompson’s small boat was launched to bring it back to the ship for recovery using the ship’s crane. After this, the next three dives proceeded normally. The Jason team and APL engineers operated like a well-oiled machine since they have a lot of experience in swapping the profiler packages at all three OOI profiler locations.
After our work at the mooring was complete it was a short one-hour jaunt from Axial Base to the caldera of Axial Seamount, where a plethora of instruments on the array are helping us understand the mysteries of this underwater volcano. The focus of this stop in the caldera was to swap an HD video camera which live streams video of the Mushroom hydrothermal vent year-round (https://interactiveoceans.washington.edu/instruments/high-definition-video-camera/), as well as an osmotic fluid sampler, which samples diffuse flow hydrothermal fluids. These tasks were completed successfully during this roughly 11-hour dive which gave us great views of a couple of the fabulous hydrothermal vents at ASHES vent field. For many of the students, as well as the researchers and engineers onboard, this was their first time seeing a hydrothermal vent in-person and such the Jason control van was crowded with an eager audience.
With Jason safely back on deck 28 hours after we had arrived at Axial Seamount we were done with our scheduled Axial work for this leg (although we will be back at the volcano next week during Leg 3). However, it turned out our job wasn’t done! During our trip from Newport to Axial at the start of Leg 2, the RCA team had started coordinating with the R/V Rachel Carson, a Monterey Bay Aquarium Research Institute (MBARI) research vessel, and R/V Sally Ride (PIs W. Wilcock and M. Tolstoy from the University of Washington), who were also planning operations in Axial Caldera during the same timeframe. MBARI was there to conduct mapping of Axial Caldera with two Autonomous Underwater Vehicles (AUVs) and the Sally Ride was there to recover and replace ocean bottom seismometers (OBSs). We were initially a little worried about the number of ships and underwater vehicles operating in the Axial Caldera area, but it ended up being lucky we were all there!
Just as we were wrapping up and about to get underway to Southern Hydrate Ridge, a call came in from the R/V Rachel Carson. One of their AUVs was drifting neutral at ~40 m water depth following a mission and couldn’t be recovered. They had attempted to send a signal to the AUV to release the emergency drop weights (which would allow the long, yellow, torpedo-shaped vehicle to float to the surface), but the request timed out. They were hoping that we could use Jason to help investigate and potentially recover the AUV.
After some quick discussions between the Captain, the Jason team, and the science team, we headed to the AUV position and began radio communications with the Rachel Carson to hand off tracking of the AUV and coordinate ship movements. Jason was launched and quickly located the stranded AUV and successfully attached a block of syntactic foam flotation to one of the forward lifting bails (a metal loop used to attach recovery and handling lines), which brought the vehicle to the surface. Jason was safely recovered to deck and the Thompson backed off the site to let the Rachel Carson successfully recover the AUV.
And our luck didn’t end there! During the AUV operation, we spotted a mysterious yellow float bobbing at the surface. We were able to relay the position information to Tolstoy and Wilcock on the R/V Sally Ride, and it turned out to be one of their OBS’s that had released prematurely. Using our position info, they were able to move to that spot and recover the instrument.
With our rescue operations completed, we resumed our transit to Southern Hydrate Ridge, a methane seep along the continental margin, where we are running a series of dives to swap and recover cabled and uncabled instruments. Never a dull minute at sea!