Preparing for Pressure Dives

Dr. Nooner, what is the most challenging part of preparing for this type of survey?

“The most challenging aspects occur before we ever go in the water—cruise planning. For example, before coming out to sea we have to make sure the instruments are completely working because once we are out here, it is impossible to get spare parts and tools that we don’t bring. We have to carefully plan out mooring, instrument deployments, and sampling operations. To do all this we need to work with the Jason team prior to coming out to ensure that the MPR instrument can be easily interfaced with the ROV. If the cruise preparations have been done properly, then success will depend primarily on only the weather, ship and ROV problems, and other unexpected problems…which pretty much always occur.”  – Dr. Nooner

From the beginning of this trip, our group has been making sure that everything would be set for our long 5-6 day pressure. We will be making pressure measurements on top of concrete benchmarks that we’ve put on the seafloor. The benchmarks we use are basically small concrete tables; each one has a painted number and a rectangular indention. The numbers allow us to differentiate them from one another on the seafloor and each one is located in it’s own region, mostly within the caldera. The black rectangular indention on each benchmark is precisely the right size so that the mobile pressure recorder (MPR) fits nicely within, allowing us to place the MPR in exactly the same place each time we make a pressure measurement on a benchmark.

Shawn and Elisa attaching a flag to one of the benchmarks.

Shawn and Elisa attaching a flag to one of the benchmarks.

Since we are installing six new benchmarks during this cruise, we had to attach the flags to each one, rig a short mooring, and then deploy them to the seafloor. We put strips of the super reflective reflexite tape on the flags to make them easily visible on the seafloor. The moorings are a series of ropes, chains, glass ball floats that are connected together and to a benchmark. These floats decrease the weight of the benchmarks (which are about 300 pounds in air) so that they can easily be moved by the ROV Jason. Once each benchmark is found and moved to its permanent location, Jason pulls a pull-pin to release the mooring with the floats back to the surface, where it is recovered by the deck crew.

On all surveys prior to this cruise, measurements have been made using one MPR at each benchmark. However, this time we will be using two MPR’s simultaneously (we are calibrating a second instrument). To achieve this, we strapped the two instruments together, one on top of the other, and rigged a handle on the top of them to allow Jason to easily pick them up and set them on each benchmark. Both of the MPR’s are connected to cables that transmit the measurements back to the surface in real time, where we will be sitting in the Jason Control Van recording the incoming data and monitoring the instruments.

Shawn and Elisa helping assemble one of the moorings.

Shawn and Elisa helping assemble one of the BPR moorings.

Since the instruments will be at the bottom of the ocean (which is about 2 degrees Celsius), it is important to have them acclimated to a colder temperature prior to the dive. A few days ago, we scrounged around the ship looking for an empty cooler or some sort of container to store the MPR’s. We found a plastic trash can, put the instruments inside, filled it with ice, and placed the whole thing in the walk in science freezer on board.

After all the steps we have taken to prepare for the pressure dive, everything is set and ready to go. Today is the day! We are about to head out on deck to plug in the MPR’s on Jason and set up the instruments. Once that is finished, he will be ready to launch at 16:00 local time!

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