PORTLAND, Ore. – Far off the southern coast of Africa, where the Indian and Atlantic oceans meet, a long line of moored buoys equipped with high-tech sensors awaits subtle changes in temperature that could affect farmers all the way to Europe.

The purpose of the buoy line streteching more than 600 miles across the sea is to help researchers determine how the flow of warm, salty water from the Indian Ocean affects the cooler, less salty Atlantic Ocean. The exchange influences rainfall and climate, but little is known about the cycle of currents that push heat from one ocean to the next.

“We do know the Atlantic would be colder without it, so we have lots of evidence the system fluctuates,” said Deirdre Byrne, a University of Maine oceanographer and visiting professor at the University of Cape Town in South Africa,

“But as a practical matter, how do you measure something that happens in a fairly remote area? We know almost nothing about how it fluctuates.”

Byrne’s research was among the topics discussed by several hundred scientists in Portland this past week at the biannual ocean science meeting sponsored by the American Geophysical Union.

Vast expanses of the ocean are still a mystery, but marine researchers are joining forces to open a new era of discovery to help manage global problems such as climate change and the food supply. “There really are huge areas that are still unexplored and so much we don’t know,” said Byrne.

Much of the discussion was about new ways of collecting information about the sea, like Byrne’s project.

“The direction of heat and salt in the ocean is very important because it controls rainfall and determines the climate,” Byrne said.

Some measurements that are relatively easy and routine on land are extremely difficult at sea – even something as simple as measuring rainfall.

But University of Washington oceanographer Jeffrey Nystuen, who trained as a physicist, has come up with a way to use the sound made by raindrops to estimate rainfall on sections of the ocean.

“Bubbles trapped in the splash of raindrops ring like tiny bells,” Nystuen said. “So the sound of even light drizzle is really quite loud.”

A submerged hydrophone captures the sound of rainfall, stores it, and then transmits the data when it bobs to the surface or is retreived by ship. A computer program breaks down the sound to indicate the pattern of rainfall and give an estimate of volume, he said.

Underwater sound can be a problem for some marine life, however, especially if it is generated by ships or other manmade sources.

Douglas Biggs of Texas A&M University is working with the oil and gas industry to protect endangered sperm whales by reducing the noise created by seismic testing during undersea exploration.

Whale behavior appears to be affected when sounds exceed 180 decibels, also a concern for military testing, Biggs said.

Hydrophones attached by suction cups to the whales helped researchers track the animals and chart their behavior using industry ships that cost $20,000 to $30,000 a day to run but were donated to the scientists for two to three weeks.

Other new approaches to charting the behavior of marine animals includes a study on the population of krill led by Peter Wiebe of the Woods Hole Oceanographic Institution.

Krill are tiny, shrimplike crustaceans that form the basis of much of the food chain in Antarctica.

Wiebe has constructed sophisticated equipment called the bioacoustic sensing platform and relay system – equipment about the size of a small car – that can be towed behind a ship to detect the different acoustic signals of krill and other tiny marine life.

The pioneering project is the first major attempt to reliably estimate the size, range and movement of animals as small as krill.

“Nobody has watched what krill are doing under the ice before,” Wiebe said.

The scientists hope their collective efforts will pay off with advances in many areas of research, ranging from biomedical research to earthquake prediction.

“The exciting thing about this meeting is that it brings together so many diverse groups of scientists to look at problems from a multidisciplinary perspective,” Biggs said.

“We used to be doing it just with ships, and now we’re doing it with everything from computers to satellites,” he said.



On the Net:

American Geophysical Union: http://www.agu.org/

AP-ES-01-31-04 1453EST



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