Feb 1: Survey
“We’re looking for a flat place with mud,” says Becky.
It’s early on the evening of February 1st, and we are approaching sampling site 3. The seas have been wild today, with waves as high as 10 feet. The ship has slowed as we approach the site, and Becky confers back and forth with the Bridge via telephone to determine the best way to survey the area, taking into consideration the “sea-state” (the direction of the waves and wind) and the information we need from the survey.
We need an area that is flat enough to deploy the megacorer and retrieve the samples of diatomaceous mud (mud filled with fossil diatoms) we so desire. Using existing “multi-beam” data maps—high resolution maps of the sea floor—we have preselected a section of the seafloor that looks promising. Now, we use the echo sounder—the Chirp—to more closely examine the area for its suitability.
When you’re on the Main Deck, about every 8 seconds, you’ll hear the Chirp. Though it’s constant, it’s easy to tune it out after a while—it sounds a bit like a bird outside an open window, letting out a single long note.
The data from the Chirp produces a graph, and at survey time, Becky and many of us gather around it in the forward dry lab. Becky and Frankie—a graduate student from Lamont Doherty Earth Observatory/Columbia University—study the readout as it feeds across the screen. We want to see a lot of black and grey (vertically), indicating that that the pinger (Chirp) is penetrating deep into the seafloor. This indicates that there is sediment/mud. If it were rock, the signal would not penetrate and would simply bounce off—those sections of the graph would lack the darkness and depth on the graph.
The ETs (Electrical Technicians) are on the spot, fine-turning the Chirp and helping us get the best image/data possible.
Meanwhile, Becky, as well as coordinating with the Bridge, also coordinates with the Marine Projects Coordinator (MPC). Together, they determine when the Marine Technicians will need to be ready and out on deck to prepare the oceanographic equipment.
Considering the survey’s needs and the sea-state, the Vessel Master (captain), sets a course for the survey. It looks like a cross with two ends joined:
We have to sail across the survey area in two directions to ensure it is flat in both directions. It would be nearly pointless to survey in one direction only, as we might find it is flat in that direction but steep-sided in the other. If the megacorer hits a steep slope or all its tubes don’t make contact with the sea floor, they won’t “fire” and collect mud. We need to find a place wide and flat enough area to successfully deploy the megacorer so that all its tubes have the best chance of landing on a flat muddy surface.
Considering today’s rough sea-state and wind direction, the captain decides on a late adjustment to the order we’ll travel to these points. This will provide a less difficult and more comfortable transit for all aboard.
The MTs (marine technicians) also come by the forward dry lab, eager to find out what they’ll be called upon to do this evening and when. The MPC wants to ensure his team is able to carry out their duties efficiently, successfully, and—above all—safely. There is also a winch operator who will sit in the Aft Control Center and drive the winch that lowers the cable to which the megacorer is tethered.
The science team now has a long wait until the core comes on deck. They watch the monitors, ready to stay up late. When the megacorer arrives on deck, the scientists get dressed in their personal safety gear, help take the cores off the megacorer, and process them.
Successfully deploying and retrieving oceanographic equipment to gather samples and/or data is truly a coordinated team effort, and I’m impressed by all concerned, who work such long hours in what can be quite physically and mentally challenging conditions.
All the data lead us to believe there is a flattish, domed-shaped area of seafloor just where we expected. In this case, the survey has yielded a success!