Certain electric cruise ships create a different type of underwater noise

Marine traffic causes noise that can affect marine life. Though this is often assumed to be low-frequency sound, Bonnel et al. monitored the mid-frequency tones and narrowband sounds generated by Azipods, recent propulsion systems used on some electric cruise ships, in the Antarctic Peninsula.

“We know tourism is growing in Antarctica, and there are more boats. More boats mean more underwater noise,” said author Julien Bonnel. “Our main motivation is to quantify how much tourism contributes to the underwater soundscape out there and evaluate the potential impact on the ecosystem.”

The researchers collected passive acoustic data in Charlotte Bay and the Errera Channel during the height of the tourist season and compared the mid-frequency acoustic signatures they picked up with ship tracking data to identify the sources of noise. In 31 of their 35 detections, an Azipod-equipped electric boat was the only boat nearby; in the other four, it was the closer of two boats in the area, making Azipods the primary contributor to the data in every case.

The sounds generated by Azipods dominate the ocean soundscape for at least 5 kilometers, sometimes much farther — which introduces new questions about how the acoustics from these boats affect nearby whales and seals and whether using traditional diesel engines to create low-frequency noise instead would modify the impact on the ecosystem.

“There’s a tradeoff here. It may be good to spread the pain over a wide frequency band, or maybe not, because we may impact animals that are more sensitive,” Bonnel said. “We simply don’t know yet.”

The group has additional underwater acoustic recorders placed in the area, which they hope will acquire baseline measurements when there is less tourism. They also note the importance of monitoring the full fleet footprint of these boats and performing controlled experiments to better characterize Azipod noise.

Source: Azipod-equipped vessels in the Antarctic Peninsula radiate underwater continuous mid-frequency narrowband and tonal sounds,” by Julien Bonnel, Alex Mira, Alessandro Bocconcelli, and Daniel Zitterbart, Journal of the Acoustical Society of America (2026). The article can be accessed at https://doi.org/10.1121/10.0046465 .