High Waves and Deep Sonar

Unlike Leg 2, where we had almost creepily calm conditions, Leg 3 once again began with unfavorable weather. Even staying in port one extra day didn’t prevent us from leaving Newport in rough seas with blustery winds. There were many happy, smiling faces as we headed out under the bridge, everyone eager to get going after our extra-long port call. However, pretty soon many folks, students and scientists alike, took to their beds or went out to the high bay for some fresh air to battle their seasickness. Though most of the students on Leg 3 also sailed on Leg 2, with only one new UW student joining the group, the smooth seas during the previous leg had not prepared them for our rough transit out to the base of Axial Seamount.

VISIONS’23 science party and students on the way out of Newport to begin Leg 3. Credit: M. Elend, University of Washington.

While people perked up when we got on station and the ship was able to better angle itself to the waves for a smoother ride, the swells were too much for us to begin any operations. Our first seven hours at Axial Base were spent assessing the weather until it finally looked good enough to do a deep CTD cast around 2140 local time. The data and water samples collected by the CTD cast will be used to verify instruments on the Deep Profiler, which will be turned on Leg 4.

Launching a late-night deep CTD cast to collect verification samples near the Axial Base Deep Profiler mooring. Credit: P. Armitano, University of Washington

With the weather conditions still uncertain for diving until the sun is up, we moved about an hour and a half northwest to talk with an uncabled acoustic transponder (aka FETCH tripod) while we wait for the sun to rise. These tripods (part of an NSF-funded project led by UW scientist William Wilcock and APL engineer Dana Manalang) form an acoustic network designed to measure horizontal stresses and motion of the seafloor. By measuring the inflation of the underlying magma chamber, they could collect data that would indicate a potential eruption of Axial Seamount (which is an active, underwater volcano). The network was designed so that the three uncabled FETCH tripods would communicate with one cabled tripod at the Central Caldera site to send the acoustic data back to shore in real-time. However, the cabled tripod is currently offline, so we were able to hold position over the uncabled tripods and use the ship’s USBL (Ultra-short baseline acoustic positioning system; normally used to help the Jason ROV navigate on the seafloor) to download data from instruments 1500 meters below us. With assistance from the Jason group and APL engineers, we were able to download data from two of the three tripods, and Dr. Wilcock is currently grabbing files from the third while on the R/V Sally Ride, which has been deploying ocean bottom seismometers (OBS) in the caldera this week as well.

The aft deck of the Thompson as we left Newport to start Leg 3 of V23. Credit: M. Elend, University of Washington

Now that the weather has settled down a little, we’re preparing for the first dive operations of Leg 3, and hopefully we’ll be finished up at Axial Base sometime tonight and then starting dives in the Caldera and visiting hydrothermal vents!