June 26, 2009
56° 15.2748 N
I was up at 21:30 last night. After a quick shower and some leftovers from the galley, I was down in the lab by 22:00. The traps were scheduled to be deployed at around 02:00 and the tubes needed to be filled with brine.
A standard CTD went out at around 01:00. Pat, Matt, and I sampled for small volume thorium and grabbed an additional three samples to act as tracers. A known amount of Th-230 is added to these three extra samples and then they are processed the same as the others. This acts as sort of a reference, or measuring stick, as to how efficient the process they are using is to collect all of the thorium. A correction factor can then be applied to the data gathered.
The sediment traps were deployed without incident and floated off into the night at 02:30. It was then back to the lab to tend to the thorium filtrations and wait for the next round of CTDs. I took this time to prepare my Styrofoam cup for a journey to the bottom of the ocean. A long-standing custom on oceanographic cruises into deeper waters, pieces of Styrofoam are decorated and secured to the CTD in mesh bags for lowering to the bottom. Under the tremendous pressure, all of the air is squeezed from the Styrofoam cup and it shrinks significantly in size. I decided not to get too artsy and just marked mine with the date, latitude, longitude, and depth of the cast. A picture was taken and a ruler drawn on the side (Tracy's suggestion) to allow for an easy reference as to how much the cup had shrunk. Close to two dozen cup made their way to the bottom today to serve as souvenirs of the TN-250 cruise for scientists and crew members.
Station 54-NP15 was a deep water station, just past the continental slope. With over 2700 meters of water to sample, the CTD would be lowered twice, once for the bottom up to 300 meters, and a second time for 300 meters to the surface. Many more people are interested in the near-surface water and ours was the only group sampling off the deep-water cast. The filtrations from the earlier CTD had just finished and we quickly started the new batch. It was then back to the CTD garage to gather my samples for Dr. Lomas's pigment experiment from the Prod CTD. Thankfully there was not much in the water column here and the filtrations finished quickly.
I was able to get a nice three-hour sleep in before the traps were recovered at 22:00. Overall, the deployment and recovery of the traps went significantly smoother than the first time around. The ship's crew had now been through the procedure once before and mistakes were not repeated. 20 tubes went out and 20 tubes returned fully intact. Back in the lab the collected samples were allowed to settle for one hour and the filtering began. Salinities for the samples were in the 70s and low 80s for the most part indicating a very good retention of the brine at the bottom of the tube. No Phaeocystis bloom this time meant faster filtering which was good news considering the next deployment was scheduled in two days' time. I finally went to sleep by 03:00 on Sunday.