Navy lends its ears to high-tech whale watchers

August 23, 1993|By New York Times

It is hard to track the blue whale, at up to 170 tons the ocean's largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio beacons to the behemoth is difficult, and visual sightings are too sporadic to give real insight into its behavior.

So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, doing nothing more intrusive than monitoring its sounds. The feat was possible because of the Navy's formerly top-secret system of underwater listening devices spanning the oceans.

The whale, nicknamed Old Blue, was followed as it swam southward in the Atlantic Ocean from an area off Cape Cod to Bermuda, Florida and back again to an area north of Bermuda. All told, a trek of about 1,500 miles was closely monitored.

"It's a big deal," Adam S. Frankel, a marine biologist at Cornell University, said of the Navy's surveillance system. "It's got the potential to completely revolutionize everything we do."

Tracking whales is but one example of a heady new world just opening to civilian scientists after the Cold War as the Navy starts to share and partly unveil its global network of underwater listening gear, built over the decades to track the ships and submarines of potential enemies. The system is estimated to have cost $15 billion.

Other scientists have proposed to use the network for tracking ocean currents by listening to the beeps of drifting buoys, measuring changes in ocean and global temperatures by watching for shifts in the speed of sound in water and receiving acoustic data from remote sensors designed to detect such things as tsunamis and chemical spills.

The Navy, in a statement, called the surveillance system "an unmatched acoustic observatory" for studying the world's oceans, adding that it had "tremendous potential to contribute to a variety of national agendas, both military and civilian."

The speed of sound in water is roughly one mile a second -- slower than through land but faster than through air. Most important for eavesdropping, different layers of ocean water can act as conduits for sounds, focusing them in the same way a stethoscope does when it carries faint noises from a patient's chest to a doctor's ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles.

The Navy, from the earliest days of the Cold War, worked hard to exploit such properties. The effort evolved into the listening system known as the Underwater Sound Surveillance System, which consists of long chains of underwater microphones planted on continental shelves. The physical separation of these undersea ears allows analysts and computers on shore to estimate the bearing, depth and distance of a source of sound.

The results of the Navy's sharing of the listening system with civilian researchers is often stunning. Last November the Navy began working with civilian whale experts, including Christopher W. Clark, a Cornell biologist who had pioneered a technique using sounds for counting bowhead whales as they migrate under the Arctic ice.

Clark helped train Navy technicians, who proceeded to log tens of thousands of whale contacts. The civilian scientists, to their surprise, discovered a din of whale songs and sounds not unlike the animal noises that fill the air of any forest.

Ultimately, the listening program may help solve the fundamental mystery of why whales make the sounds they do. Some scientists believe these may be partly for communication, and partly for use as a kind of low-frequency sonar that helps them navigate or find food.

In the future, the Navy's surveillance system may help settle the question of whether the planet and its oceans are growing warmer.

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