Cold War era of SOSUS development

The Cold War is a continuing technological presence in the novel: a period whose military projects leave behind tools for listening to the ocean, mapping it, and using marine animals for strategic work. Its end does not erase those systems. Instead, they pass into scientific research, new military programs, and the crisis response to the ocean’s unexplained changes.

Surveillance systems repurposed

SOSUS began as an instrument of Cold War naval surveillance. The US Navy installed the worldwide network of sensitive hydrophones in the 1960s to monitor Soviet submarines. After the Soviet Union collapsed, SOSUS was declassified in 1991, allowing NOAA scientists to use its recordings. A system built to listen for a military adversary thus became a source of evidence about the wider acoustic life of the sea.

The recordings made the ocean’s apparent silence untenable. Sounds below sixteen hertz were so powerful that researchers had to play them back at sixteen times their original speed to make them audible to people. At that altered speed, underwater earthquakes sounded like thunder, while the calls of humpback whales resembled birdsong; blue whales’ messages could be heard across hundreds of kilometres. Much of the annual recording was instead dominated by the regular rumble of oil-industry airguns. The inherited surveillance network revealed not a quiet frontier, but a densely sounded environment already shaped by industrial activity.

That acoustic legacy becomes relevant amid the novel’s marine anomalies. A submersible detects a sound shortly before a luminous cloud forms, and SOSUS is raised as a means of making otherwise inaudible underwater signals available to human observers. Its Cold War origin therefore gives the crisis a distinctive irony: a system intended to detect hostile submarines helps people attend to phenomena that do not fit the old categories of enemy, vessel, or weapon.

Marine mammals and strategic competition

The military use of marine mammals forms a second Cold War inheritance. During the rivalry between the United States and the Soviet Union, both powers sought to develop effective sea-mammal fleets. Soviet-trained dolphins, sea lions, and belugas were taught to find mines and recover lost torpedoes, and were reportedly used to defend warships in the Black Sea. After the Soviet Union collapsed, the animals were transferred to an oceanarium in Sebastopol. There, some performed for audiences until their owners could no longer afford food and veterinary care; some dolphins later went to therapy centres, while others were sold to Iran, where their subsequent use was uncertain.

The military rationale for training such animals depended on abilities that human divers and machines could not readily match. Tests cited in the novel found that dolphins located mines twelve times faster than divers, while sea lions at naval bases in Charleston and San Diego detected torpedoes with a reported success rate of 95 percent. Dolphins could use echolocation in darkness, and marine mammals could make repeated dives to considerable depths. These capabilities made them useful in dangerous underwater work, but also placed animal perception and mobility inside military systems designed around human objectives.

The rivalry’s end does not bring an end to the programs. The US Navy Marine Mammal Program remains active, and the novel describes indications of renewed military use in Russia, a breeding and training program begun by the Indian Army, and similar initiatives in the Middle East. The reported record of only seven US Navy dolphin losses in thirty years underscores the operational appeal of the animals while also making their treatment as replaceable assets part of the story’s larger tension between intelligence and control.

After the rivalry: data and continuity

The novel also marks the Cold War’s aftermath through the release of military mapping data. In 1995, after the Cold War had ended, the American military began releasing Geosat maps, and the satellite system was replaced by newer satellites. Karen Weaver can draw on the resulting ocean-mapping records, which provide a history of observations from the mid-1990s onward. The data are not perfectly uniform: radar altimeters can mistake thick mist for the sea surface, and readings sometimes conflict. Yet their broad agreement allows Weaver to test whether ocean changes are local or global, and ultimately to confirm that Lukas Bauer’s concern about disrupted circulation is justified.

This shift from restricted military information to scientific use does not mean that technology has become neutral or fully transparent. The book repeatedly places observation within structures of access, interpretation, and authority: a network may be declassified, a data archive may become available, and yet the evidence still requires scrutiny before it can support a conclusion. The Cold War’s legacy is therefore not simply a store of useful instruments. It is also a history of knowledge first gathered for strategic purposes and later made available for questions its designers did not set out to answer.

The Cold War as an unfinished frame

Across these examples, the period is defined by systems that persist beyond their original conflict. Hydrophones move from submarine surveillance to scientific listening; military animals become objects of continued strategic interest; satellite records help researchers recognize planetary-scale change. The old competition supplies both capabilities and habits of thought, including the impulse to treat the unfamiliar ocean as a space to monitor, master, or defend against.

That inheritance sharpens the contrast between surveillance and understanding. Instruments can detect sounds, map surfaces, and report the apparent position or movement of objects, but those measurements do not by themselves explain what is happening in the sea. The novel’s crisis exposes the limits of carrying military categories into an ecological encounter: signals and anomalies may be measurable without being readily classifiable as hostile action. The Cold War thus functions not as distant background but as an active layer of the present, shaping what humans can observe and how readily they turn uncertainty into a problem of security.