VISIONS 15

From July 4 to August 7, 2015, the R/V Thompson and remotely operated vehicle (ROV) ROPOS conducted operations on Legs 1-3 of the NSF OOI Regional Cabled Array Cruise (TN326). ROPOS, operated by the Canadian Scientific Submersible facility, completed 55 dives over the 35-day cruise. All objectives for TN326 were completed. Thirty two undergraduate and graduate students participated in the VISIONS at-sea experiential learning program.  

Leg 1 focused on turning infrastructure at Slope Base, Southern Hydrate Ridge, the Oregon Endurance Offshore site, and at the base and summit of Axial Seamount. Leg 2 focused predominantly on installation and turning of the Deep Profiler moorings at Slope Base, the Oregon Endurance Offshore Site, and at the Base of Axial Seamount. Leg 3 focused on turning infrastructure at the Endurance Oregon Offshore and Shelf sites. A total of ~ 3 operational days was lost due to weather: much of this time was used to conduct ship-based operations that included EM302 mapping and CTD operations.

A total of 130 instruments and 13 platforms were installed. This infrastructure includes:

• 3 instrumented shallow winched profilers on the Shallow Profiler Moorings hosting a total of 51 instruments were recovered and reinstalled at Slope Base, the Oregon Endurance Offshore Site and Axial Base
• 3 instrumented platform interface controllers on the Shallow Profiler Moorings were recovered and reinstalled at Slope Base, the Oregon Endurance Offshore Site and Axial Base
• 3 Deep Profiler Moorings were installed at Slope Base, the Oregon Endurance Offshore Site and Axial Base, each hosting an instrumented Mclane wire crawler (the Mclane Profiler was recovered from the Axial Base mooring)
• 2 instrumented low-power junction boxes were recovered and reinstalled, each hosting 6 instruments
• 2 Benthic Experiment Packages each hosting 8 instruments were recovered and reinstalled at the Oregon Endurance Offshore and Shelf Sites.

Leg 1 (July 4-20) Highlights:

• Recovery and installation of the Shallow Winched Profilers and instrumented Platform Interface Controllers on the state-of-the-art Shallow Profiler Moorings at Slope Base and Axial Base (36 instruments total).
• Recovery and installation of two flow meters, a cabled mass spectrometer and osmo fluid sampler at Southern Hydrate Ridge, as well as fluid and sediment sampling.
• Turning of the LJ01A (Slope Base) and LJ03A (Axial Base) low-power junction boxes and associated instruments.
• Turning of the cabled HD Camera and osmo sampler at the ASHES Hydrothermal Field and cabled mass spectrometer, digital still camera, temperature-resistivity sensor, and fluid and DNA sampler in the International District Hydrothermal Field.
• The completion of numerous CTD’s for verification of instruments on the Shallow Profiler Moorings.

Leg 2 (July 20-30):

• Recovery and installation of the Deep Profiler Moorings at the Oregon Endurance Offshore site and Axial Base and installation at Slope Base
• Installation of the HPIES instruments at Slope Base and Axial Base.
• The completion of numerous CTD’s for verification of instruments on the Shallow Profiler Moorings.
• The discovery and documentation of a substantial new seep site in north of the Oregon Endurance Offshore site by a 1-year out UW Oceanography undergraduate student Brendan Philip.
• The first delineation of the April 24th, 2015 Axial Seamount eruption using the Thompson’s EM302 system. The flow is > 7 km long and up to 127 m thick. EM302 data indicate that the eruption also occurred in Axial caldera north of the OOI cabled infrastructure. The flow is mostly <10 m thick in this area, nearing the resolution of the EM302 system. However, its presence is consistent with warm water detected within the caldera by cabled OOI instruments, and by the presence of fine glass shards on a bottom pressure-tilt instrument in the Central Caldera site, as well as cloudy water in this area.

Leg 3 (July 30-August 7):

• Recovery and installation of the Shallow Winched Profiler and instrumented Platform Interface Controller on the Shallow Profiler Mooring at the Endurance Oregon Offshore site. CTD casts were conducted to for verification of instrumentation.
• Recovery and installation of the Benthic Experiment Packages at the Endurance Oregon Offshore and Shelf sites.
• Recovery of the Endurance Oregon Shelf Coastal Surface Piercing Profiler.

In addition to completing installation and maintenance tasks, during the cruise the team was able to make several scientific discoveries including the discovery and documentation of a new substantial seep site on the continental margin and the first visit to the site of the April 24th, 2015 Axial Seamount eruption. The seep was discovered by a recent graduate of the University of Washington undergraduate Oceanography program during Leg 2 of the cruise and is unlike any yet discovered. 

The eruption site was delineated using the Thompson’s EM302 system. The flow is >7 km long and up to 127 m thick (~ 2/3 up the height of Seattles’ Space Needle) on the northern rift zone of Axial Seamount. There were hints that thin flows erupted within the caldera itself.  The summit of the thickest lobe of the flow was covered by large expanses of orange bacterial mats, with more localized areas of white, filamentous bacteria in areas of more focused flow in the interstices between individual pillow basalts.

Similar to previous years, the hard work of 20 undergraduate students and one graduate student from the University of Washington, Grays Harbor College, Oregon State University, and Western Washington University significantly contributed to the cruise. The students were dedicated data acquisition loggers in the ROPOS control room and were instrumental in video and digital still image documentation of all shipboard operations, as well as documentation of all instrumentation and platforms that were installed and recovered.