How submarine cables ‘eavesdropped’ on whales

Scientists have been using submarine cables to “eavesdrop” on whales living in the Arctic. In July, a team of scientists released a study that took a practical approach normally used to monitor the cables themselves and used it to monitor the movements of Arctic baleen whales. Studies like this could change the way scientists collect data on marine life, the researchers said.

Not only do submarine cables carry Internet traffic around the world, but they have also become a common tool for scientists who collect and access data in real time. Notably, they can be used to detect earthquakes, including aftershocks that conventional seismic stations cannot. In this case, these cables are used to detect whale sounds. The study notes that this is the first instance of wildlife monitoring through a technology called distributed acoustic sensing.

Léa Bouffaut said: “Through distributed acoustic sensing, we can have better coverage. This new approach opens up new possibilities for monitoring in areas with complex sea conditions, inaccessible and without government assistance. Way”. He is a co-author of the study, a student at the Norwegian University of Science and Technology, and a researcher at the K. Lisa Yang Center for Conservation Bioacoustics at Cornell University
Whale researchers like Bouffaut typically use hydrophones to monitor the movements of underwater whales. Although the hydrophone provides high-quality data, it has limited coverage.

Hydrophones are typically deployed about 10 to 20 kilometers apart, Bouffaut explained. This relatively close distance gives scientists a good idea of ​​where the whales are, a method similar to using cell phone tower triangulation to detect where to make calls. But the ocean is so large that even a vast network of hydrophones can only observe a tiny area. By contrast, fiber-optic cables criss-cross large swaths of the ocean floor.

Distributed acoustic sensing is already used to check the health of submarine cables and can alert telecommunications companies of problems, such as line outages. It works because one of the fibers in the cable is connected to a device called an interrogator, a device that measures whether a fiber-optic cable is working properly, Bouffaut explained. The interrogator periodically sends pulses of light to the fiber optic cable. Sound or vibration can damage the cable and the pulses passing through it. By looking at changes in the light reaching the interrogator, the researchers could determine what was happening near the cable, whether it was the anchor that landed near the cable or a whale singing nearby.