Cryoacoustics Researchers Give Critical Edge to Icy Arctic Naval Operations

06 June 2025

From Dan Linehan

MONTEREY, Calif. - U.S. Navy Lt. Caroline Kelly, an officer-scholar studying meteorology and oceanography (METOC) at the Naval Postgraduate School (NPS), returned from the Arctic this past February where she conducted cryoacoustics research supporting her NPS thesis. With the U.S. Navy facing immediate challenges due to increasing adversary activities in the harsh, inaccessible Arctic, Kelly’s research aims to help improve naval operations in this critical environment.

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Research and curriculum at NPS, such as hers, has always focused on the study of the sea to gain understanding and accurately predict the operational environments critical to effective force planning, readiness, and naval resilience. This commitment to sea power ensures that naval operations maintain the combat advantage, even out to the coldest and farthest reaches of the Arctic region.

In February 2025, Arctic researchers William Jenkins, U.S. Navy Lt. Caroline Kelly, and Benjamin Reeder (left to right) conducted cryoacoustics experiments on sea ice floating in the Arctic Ocean to improve current and future U.S. naval operations in this growingly contested environment. (Courtesy photo from Mike Demello, Arctic Submarine Laboratory)

On the expedition, Kelly joined former submariner and NPS alumnus William Jenkins of Scripps Institution of Oceanography, along with NPS Department of Oceanography faculty and retired naval officers Benjamin Reeder, research professor, and John Joseph, faculty associate for research, to work with the Navy’s Arctic Submarine Laboratory (ASL).

“Since 2018, the collaboration between ASL and NPS has led to a deeper understanding of the physical properties of the Arctic Ocean,” said ASL Arctic scientist Ann Hill. “By ASL hosting NPS at the biennial Operation Ice Camp, students are afforded the opportunity to conduct independent research that provides further insight into the Arctic's physical oceanographic environment, ultimately increasing our submarine warfighting abilities.”

Though the weather conditions were ideal for the cryoacoustics measurements, the subzero temperature frosted the breath of U.S. Navy Lt. and METOC officer-scholar Caroline Kelly. (Courtesy photo from William Jenkins, Scripps Institution of Oceanography)

During the in-between years, ASL continues to venture onto the sea ice to improve logistics, test new equipment, and prepare for the next upcoming Operation Ice Camp.

Field experiments like Kelly’s align with ASL’s Arctic Exercise 2025 (ARCEX25) to support and advance Arctic operations as this maritime domain becomes more and more contested. So, ASL provided an opportunity for the NPS researchers to get onto the sea ice during the preparation period this year.

Invented by NPS faculty Benjamin Reeder, the cryophone shown on the left can detect soundwaves traveling though the ice. (Courtesy photo from Benjamin Reeder)

Two small airplanes chartered by ASL launched from Prudhoe Bay, Alaska, and flew across 155 miles of the Western Arctic Ocean to reach the ideal experimental conditions identified by the U.S. National Ice Center. They landed on an ice floe where the first-year sea ice measured 5.6 feet thick.

“Due to weather delays on land, we only did one day worth of experiments on the ice, but it turned out to be excellent conditions—beautiful skies, barely any wind,” said Kelly, despite the -20 degrees Fahrenheit temperature that frosted her eyelashes with every breath. “We got everything on our checklist, collecting so much data that we’ll be able to use it for at least the next five years!”

Inserted into a hole in sea ice, the cryophone on the right is frozen in place. Attached around its protective sleeve is a microphone. (Courtesy photo from Benjamin Reeder)

For the experiments, researchers cut holes through the sea ice in different locations. Next, they froze microphones and cryophones—invented by Reeder—into the ice and suspended hydrophones and an echosounder into the frigid water below. These instruments recorded how the soundwaves traveled below, through, and above the sea ice.

“Kelly's physics-based research lays the scientific foundation for future anti-submarine warfare capabilities, persistent multi-domain communication, and autonomous environmental monitoring for safety of navigation and Arctic Ocean prediction,” Reeder said.

The data collected adds to the improved understanding of how soundwaves travel within and between the different mediums of water, ice, and air. And as NPS continues to build upon this understanding, so do the significant advantages to the Navy.

“This was an excellent opportunity for me to connect my research with real-life application,” Kelly stressed. “I'm very thankful because I got a once in a lifetime opportunity and a chance to collect my own data, which I believe will help me interpret the results during analysis since I was there experiencing it real time.”

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