U.S., Soviet Subs on Prowl : Naval Activity Sparks Research of Arctic Region

A dramatic increase in the use of the Arctic region by Soviet and American submarines during the last two years has forced the U.S. Navy to launch a major scientific research project to learn more about the powerful forces that shape that part of the Earth.

The cat-and-mouse game that submariners have been playing there lately grew out of fears that the Soviets may have achieved the capability to launch missiles toward inland targets in the United States that have long been regarded as beyond the reach of their submarines.

Yet so little is known about a region that could play a crucial role in any military confrontation between the Soviet Union and the United States that an urgent five-year research program has been launched to delve into some of the most fundamental phenomena in that part of the globe.

Much of the research is in the area of sound propagation--how sound travels from one point to another--under the polar icecap, according to James Wilson of Granada Hills, chief scientist on the government-funded project.

In the world beneath the ice, sound waves must do the work of the eyes as well as the ears, providing the only clues about what may lie ahead in the often treacherous waters. But sound waves behave much differently under the icecap than they do in the open ocean, clouding the “picture” provided by such instruments as sonar, which is essentially an underwater radar system, and listening devices that should be able to tell the difference between the sounds made by another submarine and the sounds of ice crashing against ice.

“The transmission of sound is just totally different there,” Wilson said. “It’s just a completely different world.” And it is a world about which little is known.

“The Arctic has been a scientifically ignored area,” said Wilson, a physicist turned oceanographer. He said past expeditions to the Arctic have been “of a survival nature,” leaving giant gaps in the understanding of some of the fundamental forces at work there.

Work Restricted to Spring

Wilson and several other scientists spent six weeks near the North Pole last spring, beginning research that will continue for several years. They expect to be back in that area again next spring, the only time of the year that their work can be carried out.

“We’re on the frontier of understanding what makes the Arctic work,” Wilson said.

The research project is of such importance to the Navy that the chief of naval operations paid a personal visit to the research area last May, arriving aboard the attack submarine Trepang, which broke cautiously through the ice. Adm. James D. Watkins, the highest-ranking officer in the Navy, wanted to see first-hand how the project was going.

Watkins is a former submarine commander himself and spent several hours at the research site before re-boarding the Trepang.

Wilson and his fellow researchers found that sound waves are bent down sharply and then upward as they travel beneath the icecap, much the same as window glass refracts sunlight. The sound waves then strike the bottom of the ice and are either reflected back into the deep, or more often are scattered in many directions by the uneven surface, blurring any image that might be received by sensory devices.

Extreme Cold

He said it is not clearly understood why the sound waves are bent so extremely, but he suggested that it may have something to do with the level of salinity, the extremely cold temperatures and the high pressures created by the weight of the massive ice fields.

To learn more about it, Wilson and his co-workers drilled holes through the ice at three “ice camps” about 250 miles from the North Pole. Explosive charges of 55 pounds of dynamite were dropped through the holes and detonated.

The blast shook the ice even at considerable distances, Wilson said, something that did not go unnoticed by workers whose lives depend on the integrity of the ice.

“It’s a real thrill to set one off for the first time,” he said.

Sensors Listen

The sound of the explosion was monitored by sensors placed at various locations and at different distances from the impact area in an effort to learn how the sound waves are affected by such things as temperature changes, currents, salinity and the texture of the bottom of the ice.

The bottom of the ice field, which is floating on the ocean, is very inconsistent, reflecting the dynamic forces that mold it. For example, giant pressure ridges form on top of the ice when two fields crush together, leaving a long scar across the ice field that may rise as high as 40 to 50 feet. The surface ridges are eroded by weather, but the same type of ridges form on the underside of the ice, where they are shielded from the weather. These underwater formations, called “keels,” often extend down into the water as much as 150 feet, and that kind of formation can have a major impact on sound waves.

The world beneath the icecap is a quiet one, Wilson said, deprived of the main source of sound waves in the open sea--passing ships.

But it has its own symphony, of sorts, created by the powerful forces that shape that hostile region. That is especially true in the winter when storms grind massive chunks of ice against each other, forming pressure ridges that could be insurmountable to anyone on foot.

Rhythmic Rumbling

The formation of a pressure ridge is accompanied by “an almost rhythmic rumbling,” Wilson said.

That “rhythmic rumble,” he added, provides “certain characteristics that we can detect” with sound sensors, easily distinguishing that phenomena from the sounds made by a submarine.

Other sounds also abound in the Arctic, he added, including the sounds of life.

“The underwater sounds are replete with all sorts of biological life,” he said.

One mystery that cropped up during this spring’s research involved gray whales--which travel under the ice--surfacing frequently, as they must, in widely scattered areas of open sea where they can breathe. Yet there are many areas in which the icecap is uninterrupted for miles and miles. How do the whales know which way to go in order to be sure they will be able to surface for air when they need to?

“It’s a complete mystery to us right now,” Wilson said. He suspects, however, that whales--like submarines--depend on sound waves to ward off disaster.

Whales Understand

Like submarines, the whales must send out some sort of sound wave that bounces off structures and returns to tell what lies ahead. But whales apparently are gifted with the understanding of how those waves differ in the far north.

It is the obvious hope of Navy planners to give that same kind of discrimination to listening devices aboard submarines.

The Navy has had only limited experience in the Arctic since the historic voyage of the Nautilus, the world’s first nuclear-powered submarine, which passed under the North Pole on Aug. 3, 1958, on a nonstop voyage from Pearl Harbor, Hawaii, to Portland, England.

Navy submarines have operated in the Arctic since that time. Those operations have escalated greatly in the last couple of years with the introduction of a new generation of Soviet submarines designed to break through the ice.