SEAS Cruise 2007 : Contributed Essays
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My First Dive in Alvin, by Kate MullaughNight Ops on the R/V Atlantis
By Kyle F. Bennett, Graduate Student, Rutgers University
Kyle Bennett standing next to Towcam. Photo © 2007 C. Sheild
Ship time is very important to oceanographers and no moment at sea is wasted. On this cruise, the highest priority, of course, is Alvin and its time spent at the hydrothermal vent sites. However, there are many hours between the time Alvin is recovered in the afternoon and deployed again the next morning, and the Atlantis does not sit. During this time, a night crew of scientists and technicians use the ship for other important aspects of our research program.
One example of night operations involves what we call the elevator - a winch with a wire long enough to lower things to the seafloor. Though Alvin is a very capable deep-sea submersible, it can't carry all the equipment needed for each dive to the seafloor, all on its own. In these cases, we use the elevator to deliver equipment to the seafloor, lowering it to a location near where Alvin will visit the next day. Last night, a pump used to continuously sample water for bacteria was lowered to a location near the vents. Because the seafloor is 2500 meters down, it took several hours for the equipment to reach the bottom. During today's Alvin dive, the sub will pick up the pump and move it to a location chosen by the scientists on board Alvin.
Other research also takes place at night. I am part of a group that is taking pictures of the seafloor with a device called a towcam. This is a special camera designed to withstand the pressures found 2500 meters under the ocean's surface. The camera is attached to a large metal cage that has a big fish-like fin, which helps to keep the camera pointed in the right direction. The cage also holds special deep-sea lights, sensors and batteries to power all of the electronics. We send the towcam down using the winch until it is just above the seafloor. The ship then travels along a set path at a slow speed while the camera is towed along taking a picture every 20 seconds. Because the seafloor rises and falls, one of the technicians must pay close attention and rise or lower the winch to keep the towcam from running into the seafloor or from getting too far away to take good pictures. We also keep very good records of the locations of the towcam so that we will know the exact location on the seafloor for each picture. That way we can find the location with Alvin if something interesting shows up in the pictures. The entire towcam process takes about 10 hours, from leaving the deck of the ship, traveling to the bottom, taking the pictures, and returning safe and sound.
Once back on board all the pictures are downloaded from the camera to a computer. Each night's tow creates about 1700 total pictures! The scientists use these pictures to find new vents for study. Alvin can't search large areas of the seafloor for new vents but the towcam can.
We towcam operators usually get the towcam back on board the ship just before the rest of the scientists wake up for the day. It can be strange staying up all night and sleeping all day. Often we don't even see the other scientists on board the ship, except when we pass by on our way to bed each morning. However, knowing that we are helping to find new vents makes it all worthwhile.
