|
pack conditions
July 25, 2007 (posted July 26, 2007) by Lonny Lippsett The ice pack was dense and tight Tuesday, making it too risky to try to launch and recover the robotic underwater vehicle Puma. So the Camper team stepped up and in. “Give us an hour, and we’re ready to go in the water,” said WHOI biologist Tim Shank. The team doesn’t go into the water. Camper does. The 2812-kilogram (6,200-pound) steel-frame box—about the size of a compact car—is short for “camera/sampler.” It is lowered by a cable and winch to the seafloor and towed by the icebreaker. The team goes into a cramped, equipment-filled shipping container near the fantail. Black plastic trash bags are taped over the windows, shutting out all light—the better to see the computer and camera monitors inside. Eyes glued to those monitors—side by side by side by side—are WHOI engineers Phil Forte and John Bailey, Shank, and WHOI geochemist Susan Humphris. They are all watching video of the seafloor rolling by at 6 inches per second, for hours and hours. Fiber-optic cables bring the images up from the seafloor 4,000 meters (2.5 miles) below the surface in real time, and they allow the team to send some commands to Camper. But the team has no control of the vehicle’s speed or direction. The icebreaker Oden often has to start and stop, occasionally back up, and zigzag its way through the Arctic ice pack, which wouldn’t do for towing a vehicle. So the ship, and Camper along with it, drifts with the ice floes. “The ship is locked into the ice,” Bailey said. “Our path is up to the flow of the floes.” That’s not exactly true. A great deal of calculation goes into putting the ship in the right place at the right time. “We say we’d like to start here,” Humphris said, pointing to a spot on a seafloor map. Then meteorologist Bertil Larsson and expedition leader Ulf Hedman, both from the Swedish Polar Research Secretariat, forecast the ice pack’s drift, she said, and the crew of the Oden drive the icebreaker upstream so that the drift will take Camper over an area that scientists want to look at. What they would love to see pop onto their monitors are images of hydrothermal vents—places where hot, chemical-rich fluids seep or gush from the seafloor, supporting lush communities of deep-sea life. While the team is “Camping,” the images are also broadcast live on screens aboard Oden. For the many people who have never gone to sea before and for Oden’s crew, who have for years, but have never seen the bottom of it, watching the video is fascinating, even mesmerizing—at least for a little while. But it doesn’t change much: brown rocks, mud, and boulders going on and on. For the Camper team, focused on finding vents, it must be like looking for oases in the Sahara Desert. “There’s hours of boring stuff, interspersed with minutes of excitement,” Bailey said. The excitement comes when team members think they see something interesting emerging tantalizingly out of the darkness and into their narrow field of lights, or when they want to sample something. Camper has two samplers: one to grab solid things such as rocks or clams, and one to suction up things such as shrimp, water, and sediment. Camper has five cameras in all, one pointing up, two down, and two forward. Shank has a joystick to control the pan and tilt of the forward-looking cameras. Right over his shoulder, Humphris watches the unfolding scene, logging data. To Shank’s left, shoulder to shoulder with him, is Bailey, who has joysticks to control the samplers. “It’s like four people doing a concert,” Shank said. Phil Forte is on Bailey’s left, sitting higher up on a tall stool. (If this were a jazz quartet, Forte would be the stand-up bass player.) He has a toggle that controls the winch that raises and lowers Camper’s height above the seafloor, as well as manipulators controlling thrusters that can pivot the vehicle around. Let’s say the arc of Camper’s front lights moves onto a rock or a curious orange patch on the seafloor. Humphris assesses that it is interesting and wants to sample it. Forte moves the vehicle as best he can to put it into a good position for Bailey. Shank adjusts the camera angle as Camper keeps moving to maintain the best view of the target. Bailey times his strike to release the appropriate sampling device. “We have to decide and act quickly,” Bailey said. “When the target comes into sight, we have 10 to 15 seconds.” “There’s a lot of communication,” Forte said. “We’re talking back and forth. You have to do this as a team.” “If we want the orange thing, and we miss it, we wait for the next orange thing to come along,” Bailey said. “There’s no yelling, but there is laughing. Susan will say. ‘It’s coming up, there’s the rock I want. No, that one!’ And I’ll say, ‘Are we shopping for diamonds?’ ” “It takes a village to get a sample,” Shank joked. “We got a sample last night, and everybody high-fived each other. We keep trying to find ways to describe it. We were coming up with things like … flying in a hot-air balloon in the dark, duct-taping a penlight on a vacuum hose hanging below, and trying to suction up a marble in a field of rocks.” Camper is meant to be used once vents are found, but since ice conditions prevented Puma from searching Wednesday, Camper took a shot, drifting over an area where Puma had found evidence for a hydrothermal plume. The Camper team did not find evidence of active hydrothermal vents, but it did see features they hadn’t seen on its two previous Arctic dives. They found glassy black shards of lava, evidence of more recent volcanic activity than they’ve seen elsewhere. They saw more animals—shrimp, anemones, and sponges—which in other oceans have sometimes been found on the edges of vent fields, and occasionally in them. “We’re looking for any telltale signs of vents that we’ve seen before,” Shank said. “But at the same time, we’ve got to keep an open mind. The Arctic might be totally different.” On Wednesday, the Camper team sampled an unidentifiable orange material they saw on seafloor rocks and sediment. At first glance, Humphris, the geochemist, thought it looked “biological.” Shank, the biologist, thought it looked “geological.” Examined under a microscope, the orange material did not have mineral crystals. It also did not have spicules, needlelike calcite or silicate structures found in sponges. It didn’t dissolve immediately in hydrochloric acid, as the shells of other animals do. With no higher-resolution microscopes on board, the material remains unidentified for the moment. The scientists will freeze it to study it when they get back on shore. The other day, a visitor to the Camper van saw something on the screen and said, “What was that? Go back,” but the video just kept rolling on. “Camper can’t go back,” Shank explained, “it can only go forward.” “Just like time,” noted WHOI engineer Hanu Singh. With less than a week remaining before Oden must return to port, time is running out for the expedition to find vents on the Arctic Ocean seafloor.
|
||||
Mailing List | Feedback | Glossary | For Teachers | About Us | Contact
© 2010 Dive and Discover™. Dive and Discover™ is a registered trademark of Woods
Hole Oceanographic Institution
