Oceanography prize
By Helen Altonn
turns up in Hawaii after
7 years at sea
Star-BulletinA University of Washington ocean-ographer says he was "just flabbergasted" when he got a call from Hawaii recently about a device he put in the ocean near Japan in 1992.
Rob Wennihan, captain of the Ho 'okupu, spotted the glass object near Mokulua Island off Lanikai while on a bottom-fish survey with University of Hawaii researcher Chris Kelley.
It was a 6-foot, pole-like glass cylinder with a dome at the top. When Wennihan and Kelley cleaned off the algae and barnacles, they found the object was packed with electronic circuitry.
A tag asked any finder to inform Stephen Riser in the University of Washington oceanography department.
When told about the object, Kelley said, Riser's response was: "You have no idea what you found."
Riser arrived here last week for a vacation with his family and was waiting for a packing crate to ship the instrument home.
He said he had deployed 98 such instruments near Japan between 1992 and 1993 during seven cruises.
The project was funded by the National Science Foundation to study the deep circulation of the North Pacific.
The instrument found in Hawaii was the only one recovered -- a lucky accident.
"We weren't supposed to get them back," Riser said.
They had weight attached and were made to drift at a 3,000-foot depth for two years, then rise to the surface and become dead instruments, he said.
Seven moored acoustic sources also were placed at different locations in the western Pacific, Riser said.
The 98 instruments -- called RAFOS floats -- recorded when they heard the acoustic sources, he said.
In that way, he said, "We were able to locate these drifts once a day for a couple of years. The drifters stored (data) internally the times they heard the sources."
They were designed to shed their weight after two years, float to the surface and dump their memory to an orbiting satellite, Riser said.
"After they signaled to the satellite, their mission was over and they became a piece of garbage, basically."
Thus, he was amazed to learn one of the instruments had survived the long trip from Japan to Hawaii and had been recovered.
He figures it drifted about 1,366 miles nearly due east in two years before it surfaced in August 1994, halfway between Japan and Hawaii. Then it traveled another 2,400 miles southeast to reach Oahu.
The instruments were developed at the University of Washington and were rather delicate because they're glass, he said.
One went to the Aleutians, the rest to the west and south. "We thought they might go further north than they did," Riser said.
The acoustic sources cost about $20,000 each, and the instruments about $6,000 each, he said.
"I think it was worth the money. There are other ways to do this now, more cost-effective, but in 1992 that instrument was state-of-the-art."
Riser said the instruments had sensors that measured pressure and temperature as they drifted and they had a lot of batteries and a computer to take the observations.
They had hydro-phones to listen to the acoustic sources and transmitters that took the memory and sent it to a satellite when the instrument reached the surface.
Since oceanographers were able to get a position of each instrument once a day for two years, they could "actually see where the water is going," Riser said.
"At the surface of the ocean, it's hard enough to see where the water is going. At 1,000 meters, nobody has any idea where the water is going.
"This was really a great story about what the deep circulation of the Pacific is like."
He said he's moving on to other things now but it was "certainly a fun experiment. Every time you put one of these things in the water, you don't know if you will ever hear from it again ... "
The recovered RAFOS float may yield still more information, he said, "because people don't really know anything about corrosion, how these things age in the water ...
"I would have liked to see what grew on it."
Riser said that the batteries have to be dead, but he's curious to see if something will work when hooked up to a battery.
"We'll do something with the parts if it still works," he said.
