How Robot Gliders Map the Speed of Sound in the Canada Basin
Under the Arctic ice there's no GPS and no radio, so instruments and vehicles that talk and find their way over long distances do it by sound. North of Alaska, the water that carries that sound is changing fast: the ice is retreating, and warmer Pacific water is pushing in.
Researchers at the University of Rhode Island and the University of Washington flew two Seagliders through the Canada Basin in the summers of 2016 and 2017, more than 2,000 km of dives, to measure how the speed of sound varies in the upper ocean. Near the surface, the biggest driver turned out to be something oceanographers call spice. In this independent explainer, I walk through how it works and what the paper shows.
In the video
- How sound travels in channels: the Beaufort duct around 170 m, and a shallower one in summer
- Why a mooring in the middle of a big acoustics experiment left a gap in the top 50 m, and how the gliders fill it
- The two causes the team separated: tilt (internal waves and eddies heaving the layers) and spice (water that's warmer and saltier, or colder and fresher, at the same density)
- The main result: in the top 100 m, spice moved the speed of sound about twice as much as tilt, by the authors' count
- The shallow channel is shaken all the way through, while the deep channel's core looks more sheltered
- What the paper doesn't cover: the data are from two open-water summers, and it doesn't model what the shaking does to sound signals
- My take: anything that talks or navigates by sound in these waters works through these channels, and this paper maps where they're shaken most
The paper
"Complex upper ocean sound–speed structure measured by gliders in the Canada Basin"
Luis O. Pomales Velázquez, Sarah E. Webster, Lora J. Van Uffelen
University of Rhode Island (Oceanography; Ocean Engineering) and Applied Physics Laboratory, University of Washington
J. Acoust. Soc. Am. 159(4), 3584–3597, April 2026 (open access, CC BY 4.0)
The work was funded by the U.S. Office of Naval Research (Ocean Acoustics Program). The glider deployment was also funded by ONR (Arctic and Global Predictions Program) and Defence Research and Development Canada. The paper goes much deeper than this video: how tilt and spice are separated along surfaces of equal density, the eddies the gliders crossed, the spectra, and the results for the full dataset. If you work on Arctic acoustics or underwater navigation, it's worth reading in full.
This is an independent explainer. I'm not affiliated with or endorsed by the authors, the University of Rhode Island or the University of Washington, and the research is all theirs. The animations are my own illustrations of what the paper describes, not footage from the study, and the charts are schematic, drawn after the paper's figures. Any mistakes in the explanation are mine.
I'm Bora Celik from Piccard. I explain new research in ocean science and robotics.