What a way to finish the science component of the cruise! We did our last station this morning, station 140. We did not have any major equipment failure int he whole cruise. Here is the map for the cruise with all the stations we did. I can not believe the cruise is almost over. After so many hours of hard work by all on the ship.
All 140 successful hydrographic stations for our cruise
Today's excitement about the end of the science sampling was eclipsed by an amazing event, one that oceanographers will talk about for years and years, since it is nothing we have heard of happening before.
At the end of last week, a couple of scientists at Woods Hole Oceanographic Institution (WHOI), Dr. Bob Bearsley and Dr. Dick Limburner, hit the oceanographic jackpot. Ten years ago they deployed six moorings relatively close to the Antarctic Peninsula. Jim Ryder, who came on this cruise to deploy a mooring and retrieve others, remembers when he helped deploy those six moorings at the end of March of 2001.
Jim went back on a different cruise a year later to retrieve all the instruments, but they were only able to find five of the six moorings. The release did not work on the last one, and they were not able to find it by trolling a line with hooks on it. Luckily for Bob and Dick, they had placed an Argo float on the upper most buoy. Argo floats have a GPS and a transmitter that beams its location to a satellite.
Bob and Dick must have been very surprised last Thursday when they received notice that their mooring was beaming its location from the surface after nine years. They contacted a British research station on the Antarctic Peninsula, Rothera Station, which is relatively close to the location where the mooring was. They did not know about our cruise.
People at Rothera figured out we were in the area and contacted us about the ghost mooring that was floating around. It turned out that we were relatively close and with enough time to swing by and pick it up. After the first half of the cruise full of stormy weather, we have enjoyed a week of placid waters, which allowed us to finish the science with some spare time.
We still needed to find the mooring that was drifting. We knew where it had been four hours before our arrival to the area. We did not have an updated location because the satellite passes around these waters every now and then as it orbits earth. We had quite a few people scrutinizing the horizon from the bridge. The visibility was poor due to light fog, but the waters were very calm, which helped locate the mooring. It actually did not take long for one of us to spot the buoys.
This is an amazing story! Jim got to recover a mooring that had eluded him nine years ago. Bob and Dick were lucky to have their mooring pop up to the surface at the time in which the mooring expert that installed it ten years ago was on board an oceanographic cruise nearby and with time to spare. The recovery was flawless. Jim tried to extract the data form the instruments, but the batteries, as expected, are all gone. The instruments will be send back to WHOI for data recovery. I will be at WHOI over the summer, so I plan to follow up with what happened to the instruments!
The mooring is a time capsule itself. The two current meters are 'old style' . These are called Averaging Current Meters (ACM) because they do an average of the currents over a specified period of time. The have a rotor that spins according to the current speed. The image below shows the rotor blades on white at one end of a current meter, and the other end of the current meter in yellow.
Hydrographic station for CLIVAR S4P. I am amazed that 10 years make an instrument 'old style' until I think of what time means for a computer.
Another big difference with the mooring we recovered a month ago is the large amount of organisms attached to the instruments, floats and even the cable. There are anemones, tunicates (sea-squirts), worms, and sponges. Here is picture of an anemone on the release.
Unhappy anemone living on top of the release.
And here is one of the tunicates on the bottom half of the largest float. They are much larger than the ones I remember seeing before.
Tunicates, or sea-squirts, living on the underside of a mooring buoy.
The mooring also had an old style ADCP (old as in ten years old). The instrument and the cage are also covered with organisms.
An old style ADCP from the ten year old mooring
How did the mooring released nine years later? It seems that the release ended up working, but we do not know why now.
Now that science has been completed and we begin sailing towards Chile, the night watch is transitioning to living during the day. Some have been awake since 11:00 pm last night, and plan to go to bed until 10:00 or 11:00 tonight. Others did take a short nap. People are beginning to pack their equipment, and I have more journal entries planned than days left on the cruise…