Searching for answers at the top of the world

Turning in 10 seconds.... All stop!

"Left 15 degrees rudder!"

Lt. Vann Walke's commands briefly silence the banter in the control room as the USS Hawkbill, a 292-foot, 4,800-ton, nuclear-powered attack submarine, heels and turns to port.

Moments later, the chief of the watch announces: "Probe's away."

At another time, in another place, Lieutenant Walke's commands might have signaled the captain's interest in using ocean layers to hide his sub from the prying "pings" of hostile sonar. The just-launched probe returns data on changes in the water's temperature, density, and, indirectly, salinity with depth - factors that bear on how sound travels through water.

Today, however, the launch will draw a final set of measurements, marking the end of a successful week-long run under winter ice on behalf of civilian science. The nearly 1,200-mile trip is one segment of a three-month cruise designed to give marine and earth scientists unprecedented access to the world's least understood undersea frontier - the Arctic Ocean.

Known as the Submarine Science Ice Exercise (SCICEX), the program highlights a growing commitment on the part of the US science community during the past 10 years to understanding the intricate ties between Arctic sea, ice, atmosphere, and ecosystems - and to track the region's response to, and potential influence on, climate change.

Data from the five-year program, which ends later this month, have uncovered trends that leave researchers wondering whether they represent part of the region's natural cycles or initial signals of climate change.

*Arctic ice has undergone a 20 percent reduction in mass, although seen from the air, the ice's extent has shrunk by only 5 percent. In essence, the cap has been been melting from the underside and has thinned by an average of 1.5 feet. As a result, the ocean's salinity has measurably decreased.

*Water temperatures near the surface have warmed by more than 1 degree C over the past 10 years, as warmer Atlantic water has penetrated farther into the ocean and shifted its boundary with colder, more nutrient-laden Pacific water.

*Arctic Ocean circulation patterns appear to be more varied and complicated than previously believed. Such currents help transport nutrients - and contaminants - within the region.

SCICEX also represents an attempt by the US Navy to maintain a level of expertise in Arctic submarine operations threatened by cuts in the Navy's sub fleet and the growing list of non-Arctic missions for the boats that remain.

With the collapse of the Soviet Union and the end of the cold war, "there was a great turning of one's back on the Arctic from the military perspective," says George Newton, chairman of the US Arctic Research Commission and the driving force behind SCICEX. As a former submariner, he says he realized that the need to operate in the Arctic Ocean hadn't vanished - "and you can't understand the Arctic as a submariner without being there," he says. Meanwhile, civilian scientists "realized that they knew darn near nothing" about the region.

The blending of the two interests seemed natural, he adds, leading him to push his former Navy colleagues toward making a nuclear attack sub available for civilian research, while pulling on researchers wary of having their data stamped "classified."

First blind date

What he calls the first "blind date" took place in the summer of 1993, when the USS Pargo embarked on a "proof of concept cruise." The following summer, Navy representatives and their counterparts at the National Science Foundation, the National Oceanic and Atmospheric Administration, and the US Geological Survey signed a prenuptial agreement, and late in the summer of 1995, they tied the knot with the first of five annual cruises.

Since then, the Navy has used four 30-year-old Sturgeon-class nuclear submarines - specifically designed for surfacing through Arctic Ocean ice - to boldly take researchers where no ice-breaker-based science team has gone before.

"Ice breakers are awesome vessels," acknowledges Dennis Conlon, who heads the Office of Naval Research's high-latitude-dynamics research program, one of the key groups funding SCICEX research. "But the costs are horrendous."

Oceanographic research often requires a vessel to steam back and forth over an area "mowing the grass," as Hawkbill crew members call it. Muscling their way slowly through ice, surface ships could never cover an area as quickly or extensively as a submarine can. Nor, he adds, could they tow equipment or drop throwaway sensors with the ease and frequency of a nuclear sub, which can operate for months without surfacing.

The advantages a submarine offers, however, also entail risks in some ways as imposing as those astronauts face. A sub operates in an environment as hostile to humans as the cold vacuum of space. A malfunction in the sub's life-support systems or a fire could cost the Navy a crew and boat.

In an emergency, subs must surface quickly, taking their thick, frozen ceiling into account. Along the sub's path, crewmen - who otherwise might be entering target data into torpedo-guidance systems - watch the Hawkbill's upward-looking sonar for patches of thinner ice that the sub could break through. They plot each patch and hope they never have to return to it.

On this trip, ice also became an adversary during the sub's eight-day, thousand-mile transit through the Bering Strait.

Cmdr. Robert Perry, the Hawkbill's captain, explains that the timing of this mission meant that this SCICEX cruise would encounter the southernmost extent of winter ice. Ice cover that stretched far south of the Aleutian Islands forced the sub to run the entire straight submerged, forgoing occasional position fixes from global navigation satellites. The sea floor through the strait is smooth, he acknowledges, but it gradually rises the farther north one sails - at points reaching depths of only 160 feet. The sub is 52 feet tall from the keel bottom to the top of the stubby superstructure, or sail. Meanwhile, ice pressed south through the strait's choke point in the Chukchi Sea. Floes piled into each other, driving ice downward to form knife-edged "keels."

The ceiling dropped

At one point, Commander Perry says, the crew was forced to ease the sub beneath a keel that left a scant 13 feet above the sail and 18 feet between the ship's keel and the bottom. In other cases, deeper ice keels forced the Hawkbill to run parallel to the formations until its sonar scouted openings the sub could clear. Operating solely on gyroscopes for navigation, the sub wound up a mere mile and a half off course by the time it neared an ice camp set up for SCICEX 99, some 130 miles north of Barrow, Alaska.

"I was very nervous the whole time," Perry says, with some understatement. Chief of the Boat Gary Olivi, one of the diving officers, puts it more graphically. If he'd been gripping a piece of charcoal at the start of his control-room watch, "it would have been a diamond by the end of it."

In addition to gathering data from 135 probes that will have been launched by the time the cruise completes its 44-day science program, scientists aboard the Hawkbill have been taking water samples to study everything from the microscopic creatures to the characteristics of Arctic Ocean currents and the level of chemical contaminants.

The primary goal of this final cruise, however, is to map key features of the Arctic Ocean floor. The Hawkbill's own sonar has been augmented with SCAMP, a custom sonar array that can image the sea floor out to six miles on either side of the ship's track and can penetrate more than 600 feet into the sea floor. An allied gravity meter, which measures the density of the earth's crust, yields clues as to the Arctic Ocean's geophysical evolution by helping scientists identify which parts of the bottom originated as oceanic crust or as continental crust.

Standing in the Hawkbill's torpedo room-cum-laboratory, SCICEX 99 Chief Scientist Margo Edwards explains that an accurate picture of the bottom is of more than academic interest. "One day last week we came up over some extremely varying relief," recalls Dr. Edwards, associate director of the University of Hawaii's Mapping Research Group. At one point, a crewman took the sub's bottom sounder off-line to change the paper in its recorder. SCAMP was the only tool left for gauging the sub's distance from the sea floor.

"Suddenly, our tracker lost the bottom," she says, leaving the sub blind. When the sub's sounder came back on line, its readings and the ship's charts indicated the sub was close to striking a rapidly rising sea floor. No sooner had the control room sounded the ship's collision-alert alarm than it sounded "brace for impact."

At that point, SCAMP picked up the bottom again, showing that the sub still had sufficient clearance. It was a white-knuckle moment, Edwards allows, "and had there been decent charts of the area, we wouldn't have had a problem."

SCAMP, built with a $4 million grant from the National Science Foundation, has a stunning impact on charts. Putting together a preliminary map of a feature called the Northwind Ridge, Edwards sets the color printout beside a current chart. Where the old chart shows a feature resembling an oversized plateau, the new chart is brimming with detail, including evidence of an extinct volcano. Northwind, once charted as a single ridge, "is a double or triple feature. It's possible this fragment came from Canada," she says.

Taking the sea floor's measure

Quite apart from navigation, however, is the importance of taking the sea floor's measure to better understand how the ridges and basins affect the flow of water into, around, and out of the Arctic Ocean. In the enclosed basins, geological features influence water and ice circulation," Edwards says. These, in turn, can affect the distribution of nutrients for Arctic Ocean marine life and even local weather patterns as shifting ice opens to expose the water underneath to evaporation.

The Arctic Ocean's overall form began to emerge between 75 million and 115 million years ago, she says. "This is the only ocean basin in the world I know of where we're still asking: How did this form?"