How scientists are using global internet cables to track silent, deep-diving blue whales
In short: Blue whales are notoriously difficult to study, often vanishing from sight once they dive. While researchers previously relied on short-lived suction tags, a breakthrough using fiber-optic telecommunication cables now allows scientists to detect these massive creatures even when they are completely silent, revealing their hidden movements across the ocean floor.
For years, monitoring blue whales meant relying on hydrophones—underwater microphones that track the animals' vocalizations. However, this method fails when whales go quiet. A new approach, known as distributed acoustic sensing (DAS), turns the vast network of subsea fiber-optic cables that lace the global ocean into a massive, sensitive sensor array. When a blue whale moves through the water, it displaces enough volume to create low-frequency waves. These waves ripple toward the seafloor, causing the buried glass cables to stretch almost imperceptibly. By firing laser pulses down these cables, researchers can detect these tiny physical distortions.
The technique was validated by a team of Norwegian researchers who observed a blue whale vocalizing at the surface before diving. Once the whale submerged, the team tracked its movement via the cable’s disturbance, confirming they could monitor the animal even in its silent state. To interpret these signals, scientists applied the Rayleigh equation, a physics formula from 1917 originally designed to study collapsing bubbles. Despite the massive size difference between a bubble and a blue whale, the underlying physics of pressure and velocity fields remains consistent, allowing researchers to synthesize the whale's motion from the cable data.
This development is significant because it provides a window into the deep-sea behavior of whales, a realm where they have historically been invisible. While suction-cup tags provide high-resolution data, they are prone to falling off and offer only a limited duration of observation. In contrast, subsea cables offer a permanent, passive monitoring infrastructure. This could allow scientists to track seasonal or daily behavioral changes, potentially unlocking secrets about how whales navigate environments transformed by climate change, noise pollution, and shifting food sources like krill, which are essential to their survival.
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Sources
- Summary by Intellect · source: What Are Blue Whales Doing Underwater?
- Also: The Global Web of Subsea Cables That Connects the World Can Now Detect Whales—Even When They're Silent
- Also: Blue whales are going eerily silent—and scientists say it’s a warning sign
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