The Acoustic Footprint of Deep-Sea Mining: What It Means for Cetaceans

The ocean is not a quiet place — but it was never as loud as it is today. Shipping, sonar, seismic surveys, and industrial activity have raised ambient noise levels in some ocean basins by 30 decibels or more since the 1960s. For marine mammals that depend on sound to navigate, communicate, find mates, and hunt, this transformation of the acoustic environment is a serious threat. Deep-sea mining would add an entirely new and geographically concentrated source of noise to one of the least-studied parts of the ocean.

How Sound Travels in the Ocean

Water is an excellent medium for sound. Sound travels roughly five times faster in seawater than in air (approximately 1,500 m/s versus 340 m/s), and it attenuates far less over distance. Low-frequency sounds produced at depth can propagate thousands of kilometres through the deep sound channel — a thermocline-bounded acoustic waveguide between roughly 600 and 1,200 metres depth where sound refracts back toward the centre rather than spreading and losing energy.

Sources of Mining Noise

A deep-sea polymetallic nodule mining operation involves three distinct noise-generating systems:

Seafloor collector vehicles crawl across the abyssal plain at depths of 4,000–6,000 metres, generating continuous low-frequency mechanical noise directly against the seafloor substrate.

Riser and lift pump systems transport a slurry of nodules and seawater 4–6 km vertically to the surface support vessel. The pumps generate intense broadband noise at the seafloor, at mid-water depths, and at the surface.

Surface support vessels and shuttle tankers are large industrial ships operating continuously for months at a time.

Impact on Marine Mammals

Sperm whales are the most commonly documented cetacean species in deep-water areas that overlap with ISA mining zones. They dive to 2,000 metres or more to hunt squid using high-frequency echolocation clicks. Elevated ambient noise can mask social communication codas, disrupting group cohesion.

Beaked whales are among the deepest-diving cetaceans, regularly reaching 1,500–2,000 metres. They are known to be highly sensitive to anthropogenic noise; the U.S. Navy's sonar exercises have been linked to mass strandings of beaked whales.

Baleen whales — including fin whales, blue whales, and sei whales — communicate primarily through low-frequency calls that propagate over hundreds to thousands of kilometres. Mining noise in the 10–1,000 Hz range directly overlaps the communication frequencies of these species.

The Noise Risk Grid on Abyssal Claims

Abyssal Claims integrates underwater noise risk data from the EMODnet European Marine Observation and Data Network alongside cetacean density estimates from OBIS species occurrence records. The Noise Risk Grid shows 1° cells across the North Atlantic and adjacent seas, colour-coded by a composite risk score that combines noise intensity and cetacean vulnerability.

Regulatory Status

There is no binding international framework specifically regulating anthropogenic noise in the deep international seabed. The ISA's Mining Code includes draft environmental protection regulations, but noise monitoring requirements remain a contested element.

Enable the Noise Risk Grid layer in Abyssal Claims to see where cetacean density intersects with existing noise pressure. Overlay Mining Concessions to see where proposed extraction zones coincide with areas already under acoustic stress.