Dancing with the Weather Gods

The fantail of the Thompson is loaded with the medium-lift winch (center, yellow) and heavy-lift winch aft. ROPOS equipment is starboard. Credit: M. Elend, University of Washington, V22.

Leg 4 of the Regional Cabled Array VISIONS’22 expedition set sail on the R/V Thompson with the ROV ROPOS at 1030 am on September 6, heading 40 nm out to Slope Base to recover the Shallow Profiler Mooring, with the reinstallation planned for Leg 5. This will be the first time that a complete recovery and reinstallation of a Shallow Profiler Mooring will take place on an RCA cruise.

Two legs are required because of the large amount of gear that will be brought onboard during recovery, and then again required for the installation. Mobilization for these operations included loading of both a heavy- (16,000 lb) and medium-lift (18,700 lb ) winch to bring this two-legged mooring onboard.  Mooring components included thousands of meters of cable (the water depth at Slope Base is 2900 m), 12,000 lb anchors, and the Shallow Profiler Platform that is 12 feet across and over 5,000 lbs. This is in addition to the >150,000 lbs of gear that make up the ROV ROPOS system.  With a full aft deck, and full contingent of APL engineers, the ship arrived at the Slope Base site at 1600 local.

The Shallow Mooring Platform is winched onboard the Thompson. Credit: M. Elend, University of Washington, V22.

As always at-sea, our eyes are on the weather, and especially for this Leg because the ship is bringing up heavy packages. On the 7th, the seas were picking up but it was decided that operations would forward as there was a small "weather window" for recovery.  This operation required triggering an acoustic release, which freed one leg of the mooring from an anchor on the seafloor, allowing the 200 m-deep platform to rise to the surface. The platform was detached from the electro-optical cable leg of the mooring and at 1046, the platform was recovered on deck! It was a very long day with intense deck work, but at 1916, the EOM cable was on deck, and 94 syntactic floats and the acoustic release were all brought successfully onboard.

There was a lot of excitement onboard because the mooring platform, which was installed in 2014, had become a “biological island” with numerous organisms utilizing the surface of the platform as their home.

Corals, anemones, and sea feathers are some of the organisms that have colonized the mooring platform during its 8-year deployment. Credit: M. Elend, University of Washington, V22.

Of great interest were beautiful corals that had colonized the hard substrate of the platform – many of these were preserved for follow-on researchers on land. Other organisms included abundant anemones and sea feathers.

The weather gods are playing with us as the day ends today and the team is anxious to get the remaining equipment onboard. The next few days will be too blustery to work.  With a full deck, the plan is to return to Newport, offload the mooring gear and mobilize the new mooring for installation on Leg 5.