Power Play

CHAPTER 5 THE BERING STRAIT

Captain Wilson leaned over the navigation plot in Control as USS Michigan approached the hazardous Marginal Ice Zone. At the fringe of the polar ice cap, wave action and ocean swells broke off edges of the ice floes, creating a zone of broken ice extending outward over a hundred miles. However, it wasn’t the ice floating on the surface that concerned Wilson. It was the random icebergs scattered throughout the Marginal Ice Zone. Most of the icebergs were small, but the larger ones descended several hundred feet, occasionally deep enough to ground on the bottom of the shallow Bering Strait.

Wilson called to Lieutenant Jeff Porteous. “Officer of the Deck, set the Arctic Routine.”

By setting the Arctic Routine, Wilson had ordered additional sonar consoles manned and the Deck and Conn split, with Wilson and the submarine’s Executive Officer alternating as the Conning Officer. The additional watchstanders arrived and Wilson relieved Porteous of the Conn, announcing the turnover to watchstanders in Control.

“The Captain has the Conn. Lieutenant Porteous retains the Deck.”

The Quartermaster acknowledged and continued preparations for entering the Marginal Ice Zone. He energized the submarine’s topsounder and fathometer. The topsounder would send sonar pings up from one of four hydrophones mounted on top of Michigan’s hull: two on the sail and one each on the bow and stern. The topsounder would detect ice above and provide warning if an ice keel descended toward them. To help avoid the occasional iceberg, Michigan would run deep, closer to the bottom than usual, using the fathometer to ensure they didn’t run aground.

One of the sonar watchstanders energized Michigan’s High Frequency Array, the forward-looking under-ice sonar mounted in the front of the sail. The array sent pulses out in front of the submarine and displayed the objects ahead as colored blotches. Different colors represented the intensity of the sonar return, with red indicating a large, deep, or dense formation.

Unfortunately, ice-detection sonars were not very good at determining the depth of the object, which is what ultimately mattered. The color of the ice was key. As Michigan closed on the object, shallow ice keels would recede upward and exit the ice-detection beam. As it receded, the color would change from bright red to darker, cooler colors until it faded to black.

The ice-detection sonar used a simple geometry algorithm to determine if the obstacle was a threat. If the ice didn’t change from red to another color within a certain distance — the Minimum Allowable Fade Range — Wilson would have to turn or go deeper. The display was black; there were no ice formations ahead.

Their journey beneath the ice would be treacherous, transiting over the shallow Chukchi Shelf in the Pacific and the Barents Shelf in the Atlantic. The ice keels were still deep this time of year, leaving little room for safe transit. As Wilson prepared to take Michigan beneath the ice, he knew he wouldn’t get much sleep until they reached the deep-water basins of the Arctic Ocean.

The Quartermaster looked up from the electronic chart and announced, “Entering the Marginal Ice Zone.”

Four days later, with his submarine five hundred feet beneath the polar ice cap, Captain Wilson entered USS Michigan’s Control Room, stopping to examine the electronic chart, assessing his submarine’s transit. Michigan was traversing the deep-water portion of the Arctic Ocean, her main engines pushing the eighteen-thousand-ton submarine forward at ahead flank speed. They were approaching the Lomonosov mid-ocean ridge, which rose rapidly to three thousand feet before dropping off to an average depth of fourteen thousand feet. In the deep-water basins, Michigan could proceed at maximum speed without fear of hitting the bottom or ice keels descending from above.

Beside Wilson stood Petty Officer Second Class Pat Leenstra, on watch as Quartermaster. Leenstra was analyzing the ship’s two inertial navigators for error. Once Michigan passed 84 degrees north latitude, both inertial navigators had been shifted to Polar Mode to compensate for the reduced effect of the earth’s rotation. Traveling across the top of the world was always touchy when relying on inertial navigators. For example, when at the North Pole, no matter which direction you turned, you were headed south.

“How are we doing, Leenstra?”

“Good, sir. Both inertial navigators are tracking closely together.”

That was good news, as they wouldn’t be able to get a satellite fix until they exited from under the polar ice cap, or came across a lead or polynya. The ice cap was not a solid sheet of ice, but a piecemeal collection of ice floes jammed together by the wind, currents, and waves. The floe edges did not always meet, creating leads — narrow gaps within which submarines could surface. There were also polynyas — ice-free holes the size of a small lake, often large enough for two or more submarines to surface. Polynyas were rare, however, with submarines almost always surfacing in leads or punching through a thin section of ice.

The under-ice transit had been uneventful thus far, and it wouldn’t be long before Michigan entered the Barents Sea.

Several days later, Michigan prepared to exit from under the ice in the Barents Sea.

“Approaching the Barents Shelf,” the Quartermaster announced.

“Helm, ahead two-thirds,” Wilson ordered, stationed as the Conning Officer again.

Wilson slowed from ahead flank as they approached the Barents Shelf, where the bottom rose rapidly from a depth of fourteen thousand feet to less than seven hundred. In another hour, they’d exit from beneath the polar ice cap and enter the Marginal Ice Zone again, then continue their trek south toward the Russian torpedo.