During the 20 hr transit from Slope Base, those who could used the time to catch up on some much needed sleep and to conduct final preparations for what will be an intense few days with seven Jason dives planned. The Sikuliaq arrived at the base of Axial Seamount in the afternoon of July 24th, and completed the turn of the HPIES instrument, followed by a two hour transit to the summit of Axial Seamount. During a series of four dives within the caldera, nine instruments were turned and one medium-powered junction box. Verification gas-tight samples were taken at the Escargot and El Gordo vents, and the mass spectrometer, digital still camera, and remote access fluid and DNA sampler mooring was turned.
It was exciting to work at the hydrothermal vent sites again and observe the changes since last year. For example, a beautiful, small white, anhydrite-rich chimney had sprouted from the orifice at the Escargot chimney, embedding the wand of the temperature-resistivity sensor. The ROV measured 151°C fluids at the area where the hydrothermal ‘vent cap’ had been installed in 2014, hosting the inlet for the remote fluid access sampler, microbial DNA sampler, and mass spectrometer. Shortly thereafter, a vent water sample was taken with the isobaric gas-tight sampler during which the temperature ranged between 175 °C and 185 °C. All tasks were completed at the International District hydrothermal field.
One of the most exciting dives focused on turning of the high definition camera that had been streaming video live from the ASHES hydrothermal field to the terrestrial Internet for two years. During Dive J2-933, the camera installed in 2014, located at the actively venting Mushroom edifice, was unplugged and stored in the elevator for later recovery by Jason. The new camera was installed at nearly the same location. While Jason was observing the installation “live”, the engineering team at the University of Washington Operations Center, located in the School of Oceanography, turned the HD camera on and conducted a series of tests (lights, pan and tilt). There were some fun moments involving Jason ‘observing’ the HD camera (CAMHD) and CAMHD ‘observing’ Jason with live video fed at the speed of light from 5000 ft beneath the oceans’ surface and from >300 miles offshore.
Once all tasks were completed at the vent fields, we had the opportunity to go back to the eruption site where lavas spilled onto the seafloor in April, 2015: the thickest portion of the flow is >400 ft thick, or ~ 2/3 the height of the Space Needle. Through a NOAA-NSF-supported dive focused on recovering a RAS mooring installed at a diffuse flow site on the eruption, we were able to investigate changes in the eruption site over this past year. Most of the areas that had been covered in dense microbial mats, were no longer active, however, localized flow with temperatures of ~11-14°C were measured in small diffuse flow sites issuing from between pillow-lobate flows. At the end of the dive, the RAS mooring was released for recovery at the surface.
The final dive of Leg 2 (J2-937) was back at the International District hydrothermal field. We visited the El Gordo chimney to insure that the vent cap was in a good position for continued year-long sampling at this site. A new diffuse venting site where fluids are issuing directly out of a sheet flow was also examined as a potential site for installation of the mass spectrometer, fluid sampler and camera next year. This site, just south of the Escargot chimney, issues fluids at 94°C from a small area of tubeworms, sulfide worms and limpets with significant flow. The final portion of the dive was a quick trip to the ~ 18 m tall black smoker chimney called El Guapo. Here, close up observations at the summit of the chimney documented boiling fluids – bubbles were very clearly venting at the summit. This dive marked the end of the Jason dives for Leg 2.
During the 27th, weather continued to worsen and so the remaining time was used to conduct CTD casts at both full ocean and shallow depths for instrument verification. The shallow casts were completed while the Science Pod on the Axial Base Shallow Profiler was conducting its mission of rising up and down through the water column. Collected CTD data will be used for follow-on instrument verification. Upon completion of the CTD’s at 1542, the Sikuliaq began its transit to Newport, Oregon arriving at the NOAA dock at 1100 on July 30. The transit was rough with poor seastate and winds of 25-35 knts, with gusts to 40 knts. The team was happy to get to shore and very grateful to the NOAA facility for allowing us to dock at their facility again during the transition from Leg 2 to Leg 3.