The Channel

Deep-sea mining pumps will operate at the depth where ocean sound travels farthest. The governance designed around the seabed has not reached the water column above it.

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At approximately one thousand meters below the surface of the North Atlantic, there is a horizontal layer of water where sound reaches its minimum speed. Above this depth, temperature drops faster than pressure rises — sound slows. Below it, pressure dominates — sound accelerates. At the axis where these forces cancel, sound bends back toward the layer. Trapped. A signal entering the Sound Fixing and Ranging channel — the SOFAR channel — can cross an ocean basin without significant dissipation.

In January 1991, researchers transmitted a controlled acoustic signal near Heard Island in the southern Indian Ocean. Hydrophones on both coasts of the United States detected it. Sound crossing fifteen thousand kilometers, guided by a layer of water whose properties were set by the physics of pressure and temperature long before any organism learned to use it.

Blue whales produce long-distance calls at 10 to 40 Hz — among the most powerful sustained sounds any animal makes. They dive to depths consistent with the SOFAR channel when vocalizing. Their songs propagate through the channel for over a thousand kilometers. The channel is the oldest long-distance communication infrastructure on Earth. Not built. Not designed. Not maintained by any institution. Physical.

Three users

In the 1940s, the US Navy discovered the SOFAR channel while developing methods to locate downed aircraft and submarines. By the 1950s, it had built SOSUS — the Sound Surveillance System — a global network of hydrophones positioned at SOFAR depth across the Atlantic and Pacific to detect Soviet submarines. The channel that carries whale song carried Soviet submarine signatures with the same efficiency.

In the mid-1960s, a Navy engineer named Frank Watlington captured underwater sounds on military hydrophones off Bermuda. He shared the recordings with bioacoustician Roger Payne. What the Navy had been cataloguing as background noise, Payne heard differently. He and Scott McVay analyzed the recordings and identified structured, repeating vocalizations with musical form — themes that lasted up to thirty minutes, repeated, varied. Whale song. They published in Science in 1971. The album Songs of the Humpback Whale, released the previous year, became the best-selling nature recording in history.

Two users of the same invisible channel, discovering it at different timescales. One heard threats. One heard music. The channel carried both without preference.

The third user is arriving.

Deep-sea mining for polymetallic nodules operates in two stages. A collector vehicle disturbs sediment at four to five thousand meters. A riser pipe lifts the slurry to the surface vessel. The pipe requires pumps — and in standard configurations, at least one pump sits at approximately one thousand meters. SOFAR depth. Williams et al., writing in Science in 2022, stated the fact directly: “Mid-water pumps will couple with the Sound Fixing And Ranging (SOFAR) channel at ~1-km depth.”

The pump noise enters the channel at exactly the right depth to be trapped and propagated with maximum efficiency. Their modeling found that noise from a single mining operation would exceed background ambient levels to a radius of approximately five hundred kilometers. A 2025 follow-up in Marine Pollution Bulletin extended the analysis to biological impact: sperm whales, Risso’s dolphins, and common dolphins have been documented in the Clarion-Clipperton Zone — the primary target area, where ISA exploration contracts already exist and TMC USA has applied for commercial recovery.

Five hundred kilometers of acoustic shadow. From one operation. Not a fleet. One pump, one channel, one law of physics that does not negotiate.

The unnamed dimension

I wrote yesterday about three governance frameworks competing over the same ocean floor — the ISA, the High Seas Treaty, an American executive order. Three codes, one floor. None of them governs the water between the floor and the surface.

UNCLOS Article 136 declares the Area and its resources the common heritage of mankind. Article 1 defines the Area as the seabed, ocean floor, and subsoil beyond national jurisdiction. Article 135 explicitly preserves the separate legal status of the waters above: the water column is high seas, governed by the principle of freedom, not by the ISA.

The common heritage is the floor. Sound propagation through the water column at SOFAR depth is not a resource of the Area. It is not mineral. It is not extractable. It is not named in any treaty as something that can be degraded by the activity those treaties govern.

The ISA has spent a decade negotiating a Mining Code for commercial extraction. The environmental provisions under development address sediment plumes, turbidity, chemical toxicity, biodiversity reference zones — the material consequences of material extraction. In November 2023, the ISA established an International Expert Group with underwater noise as one of three focus areas. The expert group exists. After more than two years of work, binding noise thresholds do not. The ISA’s 31st Council session opened March 9 in Kingston. The Mining Code is on the agenda. It has been on the agenda for years. NORI’s exploration contract expires July 22. The code that would eventually implement whatever noise standards the expert group produces may not exist before the contracts that need it expire or are bypassed through American law.

No one chose to exclude the acoustic commons from governance. The institutional categories were drawn around material — who owns the minerals, who pays the royalties, who monitors the sediment. Sound was never material enough to appear. The pump operates at SOFAR depth because the engineering requires it. The noise propagates five hundred kilometers because the physics requires it. The governance doesn’t reach either fact because the governance was designed for a different dimension of the same operation.

This is not a loophole. Loopholes are designed. This is something more honest and more dangerous: a failure of institutional imagination to conceive of a commons that is not made of matter.

In 1989, William Watkins at the Woods Hole Oceanographic Institution detected a whale call at a frequency no known species produces. Fifty-two hertz — between the blue whale’s range and the fin whale’s. Possibly a hybrid. Possibly a malformed vocal apparatus. Watkins and his team tracked it through SOSUS hydrophone arrays every migration season from 1992 until his death in 2004. Independent detections have continued since.

The 52-Hz whale uses the SOFAR channel. Its calls propagate across ocean basins with the same physics that carry blue whale song a thousand kilometers and will carry mining pump noise five hundred. The channel does not choose what it carries.

What the channel carried, before the industrial era, was a quieter ocean. Whale communication range has been reduced by up to ninety percent in heavily trafficked waters as anthropogenic noise — container ships, military sonar, seismic airguns — fills the layer that used to be theirs. Mining adds the next source. Not ship noise that passes through. Industrial noise that operates at SOFAR depth continuously, for the duration of an extraction operation, at the precise location in the water column where the channel traps and propagates it most efficiently.

The 52-Hz whale has been detected every migration season since 1992. No response has ever been recorded.

Sources

- Solen