By Frankie Pavia
We’ve just completed our first full station and are remarkably pleased with the results. We collected 8 seawater samples to measure helium isotopes; 20 to measure thorium and protactinium isotopes; 7 in-situ pump filters to measure particulate thorium and protactinium isotopes; 6 manganese oxides cartridges that were attached to the pumps to measure actinium and radium isotopes; and 1 box core of the ocean floor to measure sedimentary thorium and protactinium isotopes. I was going to make this paragraph into the Twelve Days of Christmas song, but 7 pumps-a-pumping doesn’t really roll off the tongue that well.
What all this means is that the first station was a smashing success for us. The only thing that didn’t quite go as planned was the 9-meter-long gravity corer coming up empty. We suspect it may have been due to the corer not being able to penetrate the hard carbonate layer we saw—about 15 centimeters thick in our box core. Nonetheless, we are delighted.
We were especially pleased that our in-situ pumps worked. We arrived on the cruise with the knowledge that the pumps would be there, but figured that somebody would be an expert on how to program them, maintain them and operate them. The pumps are essentially motors hung on a line deep in the water, drawing thousands of liters water through a filter, catching the ocean’s suspended particles.
After a week of poring over the manual, we were finally ready to deploy the pumps. It would take them 2.5 hours to descend to 3,600 meters water depth, 6 hours of pumping, and 2.5 hours for the deepest pump to return. A convenient time to have them pump is overnight. Sleep is hard to come by while on station, so six hours of pumps pumping away at depth is a great excuse to scuttle off to bed.
We were pretty nervous as to whether they would actually work. We had invested a lot of time and energy getting them up and running. What a bummer it’d be if they spent six hours in the deep ocean not doing anything because I had accidentally programmed them to pump at the wrong time, or something. Our test run the previous day had been a bit spotty, too. The flow rate of the pumps had been something like 3 times lower than it should have been.
We woke up at 4 a.m. the next day to wait for the pumps to arrive back on deck, driven by caffeine and nervous energy. Christmas had been two days previous. On Christmas Eve the crew put on a terrific party in the hangar, and the pumps had been decorated with big red ribbons. We were about to find out whether the pumps were a present we actually wanted, or if they were one of those fancy battery-powered toys you get with a list of parts that has three missing and ends up never working.
All the pumps have names. We were able to name the four new pumps after ourselves, while the other four pumps already names. Claudia, Bernhard, Sebastian, Frankie, Laura, Frauke, Jimmy and Hulda. They all seemed to have a little personality too—especially the old ones, Laura, Frauke, Jimmy and Hulda. Parts of Laura were backwards, Hulda’s screws refused to come loose, Jimmy’s pump head had missing pieces.
Claudia was the first to arrive at the surface. Immediately upon getting her out of the water, we put a shower cap over the filter holder to protect the filter from contamination by atmospheric aerosols and any dust floating around the hangar. We pumped the remaining water from the bottom through the filter, removed the filter holder and brought it to the lab. We carefully unscrewed the top, opened it up, and…
The filter was covered in particles! One by one, the pumps came up with filters that were coated by an even distribution of particles. Everything worked perfectly. Even Laura, Hulda and Jimmy, though they were stubborn above water, did everything they were supposed to do once they were submerged.
We plan to measure protactinium and thorium isotopes on the particles to learn about the kinetics of particle movement in the ocean—sinking rates, absorption coefficients for trace metals, and export fluxes. Particles are the vectors that move elements out of the surface ocean, so studying their characteristics will be crucial for understanding how things like carbon and iron are pumped and exported to the deep.
Functional pumps meant that it was a happy Christmas for us. The next full station starts this afternoon. We’ll spend 42 hours sitting in one place, measuring dissolved, particulate and sediment samples. Yesterday we had to change all the batteries on the pumps. Each pump requires 24 D batteries per deployment, and uses them all. So for every cast of 8 pumps, we use 192 D batteries. We’ll send the pumps out tonight and retrieve them at 4 a.m. again tomorrow morning.
We’re hoping these pumps are gifts that keep on giving.
Frankie Pavia is a second-year graduate student studying oceanography and geochemistry at Lamont-Doherty Earth Observatory.
