Radio Script
1998

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Icebergs and Oil Tankers
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STORY: Although it is a clear, sunny day here in Alaska's Prince William Sound, Captain Bob Desautel stares only at the sonar screen as he guides his fishing vessel past several large icebergs. The echo of the sonar pinging away on the ice ahead and the ocean floor below sounds like something out of a World War II submarine movie.

Desautel guides his boat slowly forward, using only the sonar images that show the portion of the iceberg that lies beneath the surface of the water.

DESAUTEL: "You're seeing a bunch of icebergs in the short distance but you can't quite see beyond that to where an open lead might be."

Icebergs can, and have, caused big problems for ships traveling through Prince William Sound. The danger is especially high to tankers loaded with millions of barrels of oil from the nearby trans-Alaska pipeline terminal in Valdez. Especially worrisome are icebergs that float beneath the surface of the water. Conventional surface radar can't see such icebergs.

In 1994 the 89,000-ton tanker Overseas Ohio struck just such an iceberg, tearing a 20-foot hole in the bow. Alexander Kotlarov is with the sound's Regional Citizens' Advisory Council, a group that works with the oil industry to prevent oil spills.

KOTLAROV: "No one saw anything. They just smashed right into it, and it cost about one million dollars to repair."

To keep tankers from hitting these so-called neutrally buoyant icebergs, Kotlarov is testing sonars used by the fishing industry to see if they can be adapted for use in iceberg detection.

Originally built to find schools of migrating pollock and other fish, the sonar on Bob Desautel's 167-foot trawler is today being tested to see if it can accurately detect submerged icebergs. Dennis Soderberg is the vice president of WESMAR Electronics, the company that makes this state-of-the-art fish finder.

SODERBERG: "Right now we're running the sonar at a range of 250 fathoms to the outer edge. And we're scanning forward of the boat 90 degrees and 90 degrees to starboard. We use color in our sonars. The color represents density or the strength of the echo being returned. In this case we have set maroon as our strong, most dense target being received by the transducer. And as the weaker returns come in, they're assigned a lower class color all the way down to a light blue, which is the weakest signal."

After a full day of field trials, the sonar proved a mixed success. It did detect icebergs below the water's surface. But too often, the sonar didn't provide an accurate depiction of all the icebergs in the ship's path. While great at finding schools of fish, the sonar isn't quite what Alexander Kotlarov is looking for. But he isn't giving up. Later this year he plans to test a new marine radar that is reported to be able to pick up objects as small as a bird.

KOTLAROV: "When you look at a regular marine radar and you look at all the ice and everything you see a lot of back scatter. The UHF marine radar is something new. We're going to look at a prototype. It is supposed to really pick up seagulls and things like that. When you're looking at icebergs you want to see the large pieces and small pieces, and you want to be able to distinguish which is which. We would put a unit out there that would transmit the data back to the Vessel Traffic System. When the tankers get ready to leave port, they would ask for an ice report. Instead of having an ice report from the last vessel that came in they would get a report from that particular moment. So it would have real-time observation. And we even would like to go one step further and have the signal transmitted directly to the tanker."

Although reliable sonars do exist that could detect icebergs, such sonars are only available to the military. So until a reliable iceberg detection system is developed for civilian use, tankers in the sound will be limited to just six knots—or about seven miles per hour. Tanker captains will also continue to rely on lookouts, searchlights, and their own surface radars.

As for those pesky neutrally buoyant icebergs, Kotlarov says he'll keep looking for ways to detect them as well.

OUTRO: For Arctic Science Journeys, this is Doug Schneider reporting from Valdez, Alaska.

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Related Web sites

Icebergs, Prince William Sound (photo)

"Calculation of the Size of the Iceberg Struck by the Oil tanker Overseas Ohio" (paper)

Overseas Ohio photos after collision