Jump to content

Navy sonar under scrutiny


Recommended Posts

By KATE WILTROUT, The Virginian-Pilot

© May 3, 2005



The Navy plans to create a sonar training range where its forces can learn to detect enemy submarines. But with sonar known to have contributed to some whale deaths and possibly linked to other cases of animal distress – including a recent beaching incident, shown above, on the Outer Banks - a battle is brewing.

Four months ago, as a half-dozen Navy ships practiced hunting submarines off the coast, more than 30 whales of various species stranded and died on North Carolina’s Outer Banks.


The Navy said no sub-detecting sonar had been used within 50 miles of the beach during the exercise, and officials discounted it as a cause of the incident.


Results of a government investigation are eagerly awaited – especially because the Navy is planning to create a range for such sonar training.


The swath of sea in the Navy’s sights, farther down the Carolina coast at Onslow Bay, could become the latest battleground in the clash between military training and environmental protection.


Unlike the jet landing field the Navy wants to locate in the state, a 660-square-mile training range wouldn’t involve the condemnation of private property or affect migratory birds. Exercises would be far from the public eye.


But marine-mammal experts and environmentalists worry that sub-hunting sonar could physically harm whales and dolphins. Mid frequency naval sonar is known – as the Navy has acknowledged - to have contributed to the stranding and death of beaked whales in the Bahamas five years ago .


While the Navy prepares to release its draft environmental study of the range, possibly this month , military and government officials, scientists and environmentalists are grappling with vexing questions.


How many whales and dolphins pass through the waters where ships would use the sonar? What can be done to minimize mammals’ exposure to the sonar, which can be as loud as a jet engine at take off? Which is the bigger priority, military preparedness or safeguarding mysterious creatures of the deep?


The Navy says it must train crews to detect increasingly sophisticated diesel submarines, which are virtually silent when they run on battery power. Experts say more than 40 nations, some of them adversaries, are thought to possess about 400 diesel subs.


Still, the service says, it’s committed to balancing training with the welfare of marine mammals, protected by the federal Marine Mammal Protection Act.


“It really becomes a matter of management, and it is a manageable problem,” said Navy Capt. William Toti , who heads the Norfolk detachment of the San Diego-based Fleet Anti-Submarine Warfare Command . “Sometimes it’s inconvenient, but we’re going to do the right thing for the right reasons.”


Others see the January strandings as an ominous sign.


“The fact that this is happening on the doorstep of North Carolina as the Navy is pushing its plans to turn North Carolina into 'sonar central’ rightfully causes us concern,” said Michael Jasny , a Los Angeles lawyer who specializes in marine mammal issues for the National Resources Defense Council .


The federal act prohibits the injury and harassment of mammals. But defining what constitutes injury or harassment, let alone proving what caused it, are tricky issues. Then there’s the difficulty of measuring the problem: If a mammal dies at sea and doesn’t beach itself or wash up, how can it be determined whether human activity caused it?


Andy Read , an associate professor of marine conservation biology at Duke University, cautions that it will take great effort to make sure mammals aren’t harmed if the range is put into use, probably no earlier than 2008 .


“We shouldn’t underestimate how much monitoring it’s going to take to make sure there are no effects, or if there are effects, what those effects are,” he said.


If the Navy’s environmental impact statement doesn’t meet experts’ standards for monitoring sonar’s impact, the matter could end up in court – like the Navy’s proposal for the outlying landing field, which a federal judge has halted, citing insufficient environmental study.


“I can tell you there are a lot of people in the coastal conservation area here who are ready for another fight,” Read said. “Hopefully this one will be a little smoother.”



Less eavesdropping,


more searching


Toti said the range, which would be almost twice the size of the city of Chesapeake , is necessary for ship-based sonar technicians to hone their skills and for patrol planes and ships to learn how to work together to pinpoint underwater threats.


The range’s main feature would be a series of cables and underwater microphones – hydrophones – placed on the sea floor and connected to the shore so exercises could be monitored.


On the range, ships would play “cats” hunting a “mouse” – a U.S. nuclear sub simulating a diesel craft, or an actual diesel submarine loaned from another country .


The “enemy” sub might hide in the crevasses of the continental shelf, trying to evade detection.


That’s different from the Cold War submarine game, when U.S. and Soviet nuclear subs trailed each other in the ocean’s depths, passively listening for clues that revealed the other’s location.


Now, Toti said, the threat is diesel submarines, which are cheaper and more prolific than nuclear-powered ones. In the past 10 years, because of technological advances, diesel subs have gotten so much quieter that eavesdropping through passive sonar is no longer adequate to track them.


Lying in wait in a noisy shipping channel or hiding along continental shelves that provide lots of cover, diesel submarines are elusive targets.


One of the biggest worries is that an unfriendly submarine could endanger the chokepoints of international commerce, like the Strait of Malacca or the Strait of Hormuz. Or that they could attack U.S. warships abroad.


Another concern is the transport ships that deliver the hardware of U.S. military might. Bombs, tanks and artillery are shipped overseas separately from the troops who use them.


“This isn’t just a 'let’s protect the carrier’ issue ,” Toti said. “Everything we do in the United States military flows where it needs to go – 90 percent of it – by sea.”


Cruisers, destroyers and anti-submarine aircraft actively search for submarines using mid frequency sonar, which blasts streams of sound through the ocean, returning with an “echo” that reveals underwater objects.


Ships now have no single area to practice that skill. Sometimes they do it while in transit, other times closer to a home port, Toti said.


The problem, the captain added, is that it often takes multiple attempts to get the exercise right, and it isn’t always clear why.


“When we get the training range, it’s quite possible, even likely, that the amount of anti-submarine warfare exercises will go down,” Toti said.


The Navy’s pending environmental impact statement will outline four training scenarios for the range, from basic to advanced, he said. Most would last “a matter of hours.”


Though some larger-scale exercises would be scheduled, typical exercises would involve fewer than 10 ships, and many would involve two or three, Toti said.



A history of problems



The Navy concedes that its use of mid frequency sonar contributed to the stranding of 17 whales and dolphins, seven of which died, during sonar training in the Bahamas in 2000 , an event it had initially characterized as an unfortunate coincidence unrelated to its exercises.


There are other possible links between mid frequency sonar and animal distress :


nHours after NATO naval exercises off the Canary Islands in 2002, 14 beaked whales stranded and died. Scientists later determined that 10 of the animals had developed nitrogen gas bubbles in their tissues and blood vessels, possibly from surfacing too quickly in reaction to sonar.


nIn waters off Washington state in 2003 , a Pacific-based destroyer was conducting sonar exercises at the same time a pod of killer whales was observed behaving erratically. Within a month of that drill, 14 harbor porpoises were found dead. A government report concluded that it was impossible to tell whether the whales had suffered hearing loss or whether the dead animals showed signs of acoustic trauma.


nAs many as 200 melon-headed whales in Hanalei Bay, Hawaii, came unusually close to shore and showed clear signs of stress in 2004 . A six-ship group of U.S. and Japanese naval vessels had started sonar exercises 20 miles away that morning.


The beaching of the 34 whales in North Carolina in January is the most recent incident. Skeptics refuse to dismiss the sonar exercise as a coincidence and are waiting for a National Marine Fisheries Service report to see why the whales died.


Jasny, the lawyer, said there’s little debate among scientists that active sonar can harm or kill mammals. “The only uncertainty,” he said, “is how many marine mammals does it kill?”


But even if the investigation concludes that the North Carolina deaths weren’t directly related to sonar, some think there’s still cause for alarm.


Scientists say they are becoming increasingly convinced that even if mid frequency sonar at certain strengths or distances doesn’t cause physical problems – such as ruptured eardrums, a telltale sign of acoustic trauma – it could affect mammals’ behavior more subtly, or over time.


Maybe, scientists suggest, their feeding or mating patterns change, they surface too quickly to escape the noise, or they stay under water too long.


“How often are these effects just not being detected?” asked Erin Vos , sound project manager for the Marine Mammal Commission , a government agency.


The Navy has not announced which of the three sites it studied is the top choice for the range, but it’s known that North Carolina is the preferred alternative to waters off Virginia’s Wallops Island or Jacksonville, Fla .


To limit the potential effects of active sonar, Toti said, the Navy posts lookouts to watch for whales and dolphins and delays or moves training when mammals are spotted within a certain distance. Other measures include using passive sonar to listen for mammals and doing aerial surveys before, during and after sonar training.


Whether those safeguards are satisfactory will be up to the Fisheries Service, part of the National Oceanic and Atmospheric Administration , which issues permits for the incidental “taking,” or threatening, of marine mammals.


NOAA Fisheries officials have worked with the Navy on its proposal for at least four years. Ken Hollingshead , a biologist with the agency, said the Navy and NOAA do have scientific disagreements about the point at which sonar damages mammals and how to calculate the number of animals affected. Roger Gentry , a marine biologist and acoustics expert at NOAA Fisheries, said the North Carolina site may have the least mammal activity.


Although some species probably migrate through the area, Gentry said, there seem to be few resident whales, and the area doesn’t appear to be a prime habitat for endangered right whales.


Read said the North Carolina site stretches over the continental shelf to include relatively shallow areas a few hundred meters deep to sections that may be 2,000 meters deep. The edge of the Gulf Stream passes through the site, he said.


That varied topography is a double-edged sword: The Navy wants to train in varied terrain to learn how sonar travels at different depths and water temperatures. But those same characteristics might make it more habitable for mammals looking for food in warmer waters.


Scientists said it is difficult to count mammals in the area of the proposed training range, largely because the deep-diving beaked whales thought to be especially vulnerable to mid frequency sonar can stay submerged for an hour or more and be missed by aerial surveys.


Ann Pabst , a marine biologist at the University of North Carolina-Wilmington , was involved in a yearlong mammal census at the Wallops Island and Onslow Bay sites.


The university conducted aerial surveys from September 1998 to October 1999 for a Navy subcontractor in the project, she said.


Pabst said far more marine mammals were spotted in Virginia than in North Carolina, but the survey did find bottlenose, common and Risso’s dolphins in North Carolina, as well as beaked whales and a few pilot whales.


There’s no way to get a perfect count .


“The ocean is a changeable and dynamic habitat. These animals move, and most are capable of moving very long distances,” Pabst said. “It’s just giving us a hint at what might be out there.”

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...