Andrea Shala-Esa of Reuters reports from the Applied Physics Laboratory Ice Camp: The signal sounded like crickets chirping, but the encoded message transmitted from the camp atop the frozen Arctic Ocean was music to the ears of the USS New Hampshire submarine crew.

Lucas Jackson / Reuters

U.S. Navy safety swimmers stand on the deck of the Virginia class submarine USS New Hampshire after it surfaced through thin ice during exercises underneath ice in the Arctic Ocean north of Prudhoe Bay, Alaska on March 19.

Using a digital "Deep Siren" tactical messaging system and a simpler underwater telephone, officials from the Navy's Arctic Submarine Laboratory at the camp last Saturday were able to help the submarine find a relatively ice-free spot to surface and evacuate a sailor stricken with appendicitis.

The alternative could have been a ruptured appendix, or an emergency surgery on the table in the captain's dining room, said a relieved Dan Roberts, a senior chief and corpsman who handles the crew's medical needs. "It would have been rough."

Lucas Jackson / Reuters

U.S. Navy submariners watch a display in the control room of the USS New Hampshire as it surfaces during exercises underneath ice in the Arctic Ocean on March 20.

Lucas Jackson / Reuters

A fiber-optic periscope display in the control room shows a shore party relaxing on the ice waiting for the Virginia class submarine USS New Hampshire to surface on March 20.

The low-frequency system is built by Raytheon Co, which has been working on it for several years with $5.2 million in initial seed money from the Navy.

Raytheon is the latest player trying to tackle the persistent challenge of communicating with submarines while they are traveling deep under the sea to avoid detection. Past systems have proven too complicated, and too expensive.

Lucas Jackson / Reuters

Air reduction valves for controlling the air pressure used in torpedo tubes can be seen in the USS New Hampshire as the submarine participates in exercises underneath ice in the Arctic Ocean on March 19.

The new system could revolutionize how military commanders stay in touch with submarines all over the world, allowing them to alert a submarine about an enemy ship on the surface or a new mission, without it needing to surface to periscope level, or 60 feet, where it could be detected by potential enemies.

At present, submarines use an underwater phone to communicate with associates on top of the ice or with other submarines, but those devices are little more than tin cans on a string and work only at shorter distances. Submarines can also trail an antenna once they surface to periscope depth, or around 60 feet, but that makes them easier to detect.

Lucas Jackson / Reuters

A U.S. Navy sailor looks through cans of food on the USS New Hampshire during exercises underneath ice in the Arctic Ocean on March 19.

UPDATE: You can read more about photographer Lucas Jackson's trip to the Arctic and time on board the USS New Hampshire on the Reuters blog.