A New Way to Eavesdrop on Ocean Temperature in the Arctic

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• Alex Fox- [email protected]

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New research led by scientists at UC San Diego's Scripps Institution of Oceanography finds that the travel time of underwater sounds traveling across the Arctic Ocean can be used to precisely measure ocean temperature under the region's sea ice, providing precious data on temperature variabilityin a rapidly changing environment that is remote and difficult to access. The technique, known as ocean acoustic thermometry, was originally developed by the late Walter Munkand Peter Worcester at Scripps and Carl Wunsch at the Massachusetts Institute of Technology.

The basic principle leveraged by acoustic thermometry is that sound travels faster in warmer water and slower in colder water. The technique uses this relationship to infer the temperature of the water the acoustic signal passes through by measuring the time it takes the sound to travel from one point to another. The researchers tested the method during the 2019-2020 Arctic field season with the joint US-Norwegian Coordinated Arctic Acoustic Thermometry Experiment (CAATEX). The team used six bottom-anchored moorings across a roughly 2,600-kilometer (1,600-mile) path in the Arctic Ocean to transmit and measure acoustic signals every three days. The moorings spanned the Arctic Ocean, from north of Alaska in the west to north of Svalbard in the east, and remained in place for one year.

The experiment aimed to test whether this might be a viable way to measure Arctic Ocean temperature year-round, or if challenges such as the scattering of the sound by the rough undersides of sea ice might render the signals undetectable or impossible to decipher.

"The sea-ice has dramatically thinned over the past forty years and its roughness has also decreased," said lead author Matthew Dzieciuch, a physical oceanographer at Scripps Oceanography. "We wanted to see if scattering losses have now decreased enough to enable acoustic propagation across basins by practical sound sources. And the conclusion is that it has."

The researchers found that acoustic signals transmitted across the Arctic Ocean carried clear signatures of seasonal temperature changes in the water layers beneath the ice, demonstrating that the method can track ocean temperature variability year-round - even across distances exceeding 2,500 kilometers.

Because the Arctic's sea ice blocks satellites' views and makes access via ships challenging, these results point toward a practical way to continuously monitor temperature changes in one of the most rapidly warmingand least-observed parts of the ocean. This warming and loss of sea ice coverage in the Arctic is also attracting attention from nations eyeing newly accessible shipping routes and energy resources, making tools that can monitor its ocean interior year-round even more geopolitically important.

The study, published Feb. 2, 2026, included co-authors Peter Worcester and Hunter Akins from Scripps Oceanography and researchers from Nansen Environmental and Remote Sensing Center in Bergen, Norway; Woods Hole Oceanographic Institution in Massachusetts; and the Norwegian Coast Guard. The U.S. Office of Naval Research, the Research Council of Norway and the European Union Horizon Europe Programme provided funding for the fieldwork. The U.S. Defense University Research Instrumentation Program (DURIP) provided support for the development of the required instrumentation.

Read the story in the Journal of the Acoustical Society of America: Transarctic acoustic transmissions during the coordinated Arctic acoustic thermometry experiment in 2019-2020