Sunday, November 19, 2000

Diving for science

Published in the Antarctic Sun

Most scientists in the U.S. Antarctic Program study things on or above the ground. Some even explore the sky or faraway galaxies. But a select few regularly descend into Antarctic waters to collect material and information for their research.

On average, 20 divers make 600 dives a year in McMurdo Sound, the Dry Valleys, near Palmer Station and based from the program’s two research vessels, said scientific diving coordinator Rob Robbins.

The highest number of dives recorded in any one year was 908 in 1984, Robbins said. The average dive lasts 40 minutes, though some have gone longer than 90 minutes. The water in McMurdo Sound is 28.5 F (-2C), and near Palmer it’s only slightly warmer, at
30 F (-1C).

This summer season, six research groups, five based at McMurdo and one at Palmer, will include16 divers. The GLOBEC survey of the Southern Ocean ecosystem, based on the Laurence M. Gould and Nathaniel B. Palmer research vessels, will have two groups diving in March.

Less commonly, Robbins will dive to support specific projects that don’t have their own divers.

“Most groups bring down whatever dive labor they require,” Robbins said.

Scientists dive for many reasons, including photographing marine life, collecting specimens for lab work and maintaining underwater equipment.

“The facilities here are fabulous for diving,” said John Heine, the U.S. Antarctic Program’s advisor for research diving. “The diving conditions are really great. The support from Rob is really what makes it happen.”

One reason to dive in McMurdo Sound is that the low water temperature attracts deepsea wildlife to shallow water with little light filtering through the sea ice.

“The sound is fairly interesting,” Robbins said. “You see animals in the sound you would normally see in deep water, but at diveable depths.”

The depth at which wildlife are observable is important, because diving deeper than 130 feet and for extended periods is not allowed for scientific research. Deep diving is more complex and dangerous, even in warmer waters. In Antarctica, the margin of error is slimmer, so divers take more precautions.

“ We don’t allow decompression diving,” Robbins said.

That’s when a diver needs to pause on the way back up to the surface to adjust to the difference
in pressure.

McMurdo Station has a recompression chamber, originally installed in 1984 to comply with federal safety regulations for construction diving. After the construction finished, Robbins
said, station management decided to keep the chamber in case of dive accidents.

Since then, nine people have needed treatment. Four were aviators who had decompression
problems after accidents in which their airplanes depressurized at altitude. The other five patients were divers.

“Every one was a complete resolution,” Robbins said.

Robbins runs the recompression chamber with a volunteer crew of six, as well as a doctor
and a medical technician from the medical department on station.

Palmer Station has no chamber, though there is one at the nearby British base, Rothera, as well as in Punta Arenas, Chile.

Robbins works hard, though, to avoid accidents, and gives each dive group a firstaid kit and an oxygen kit.

“ We provide a lot of safety equipment,” he said.

He also ensures that science divers know how to move around underwater while wearing a dry suit, which keeps them warmer than a wetsuit would.

“It’s really the dry suit that’s different from most diving,” Robbins said.

A dry suit traps a lot more air than a standard buoyancy control device. Therefore, as
the divers change depth, their buoyancy changes rapidly.

Each season, each diver has to do a refresher or orientation dive to qualify for Antarctic diving, because some of the things are different here. For example, most underice diving courses teach divers to use tethers.

But here, the water is so clear, Robbins said, that they don’t need tethers if they appropriately
mark the holes.

“Here the visibility’s good. When visibility drops we use the tethers,” Robbins said.

There are two ways to breathe under water. If divers use scuba tanks, at least two divers must be in the water, to help each other in the event of an accident.

When a diver is breathing from a surface supply of air, the system not only permits twoway
communication between the diver and someone on the surface, but a rescuer can follow the air hose from the surface to a diver in distress. So a standby diver is still present, suited up and ready to swim, but is on the surface.

With only one diver using air at a time, they can take turns diving and being the standby diver for each other, accomplishing more in one outing.

“ You can do a lot more work,” Robbins said.

Also with surface supply, a diver is more comfortable in the water, Robbins said.

“It’s quite a bit warmer,” he said. “Your face is covered.”

Robbins said he would like to be doing more commercial construction diving, but he’s pretty happy with the science support end of things as well.

“This is a lot more scenic,” he said. “I’ve potentially got the best job in the program.”