The ocean is far from silent. Waves crack, shrimp snap and whales chant. Hydrophones now reveal another layer of sound: a steady hum that tracks a warming planet.

A 15-year data set from the Southern California Bight shows clear links between temperature swings, economic shocks and the volume of underwater noise, CBS 8 reports. Scripps engineers logged every crash, groan and song since 2008.

A marine heat wave in 2014 halved the low-frequency calls of blue and fin whales near San Diego, yet boosted them at cooler sites farther north. Even the 2008 recession slipped into the record as ship traffic — and its acoustic footprint — dipped.

Ocean soundscapes double in loudness roughly every decade.

Natural signals drown under human din

Commercial fleets have nearly quadrupled since the mid-1990s. Engines, sonars and pile drivers now double the background rumble every decade, a trend that stresses animals that hunt or mate by sound. During the COVID shutdown, researchers heard the difference: baleen whales filled the newly quiet Pacific with elaborate songs, while right-whale stool samples later showed lower stress hormones, notes Inside Climate News.

Slow steaming helps, because dropping a knot of speed trims a ship’s acoustic power by roughly one decibel, yet forecasts still point to busier lanes — and louder seas — later this century.

Physics shifts the soundscape

Sound moves faster in warm, salty, high-pressure water. Climate change alters each factor and, by extension, every path that a call or sonar ping follows. According to Discovery of Sound in the Sea, acoustic tomography exploits that link: transmit a low-frequency pulse through the SOFAR channel and the travel time yields an average temperature to within a few millidegrees.

Seismic “T-waves” from repeating earthquakes now extend the reach into ice-covered basins. Such techniques turn the ocean itself into a global thermometer.

Warming water accelerates sound, bending acoustic paths.

Models predict new echo chambers

Numerical work led by Dutch oceanographers paints a stark near-future portrait. By the 2090s, a surface lens of cold meltwater fresh off Greenland will trap ship noise in the upper 125 meters, pushing volumes up to five times present levels across busy North Atlantic routes, warns Science News Explores. More acidic water will absorb less energy at some frequencies, so anthropogenic clatter will carry farther.

The same study sees smaller but widespread boosts in the South Pacific and Indian oceans.

Hotspots emerge where sound speeds soar

Independent global mapping by Italian researchers pinpoints two “acoustic hotspots”: the Greenland Sea and the north-west Atlantic off Newfoundland. Under a high-emissions scenario, sound speed there climbs more than 1.5 percent — about 25 m s-1 — throughout the upper half-kilometer by 2100, according to a study in Earth’s Future.

Faster water bends rays differently and shrinks the shadow zones submarines once relied on, yet it may also channel damaging industrial noise toward already threatened North Atlantic right whales, reports AGU Publications.

Acidified seas absorb less mid-frequency energy, extending noise range.

A call for quieter seas

Hydrophones show that climate change does not just warm the ocean; it retunes it. Temperature, chemistry and circulation now conspire with global trade to raise the volume and rewrite the way sound spreads. The good news: solutions exist. Slower ships, redesigned propellers, voluntary quiet lanes and stronger Arctic rules already prove effective. Long-baseline listening networks supply the feedback loop: when vessels throttle back, the decibels drop.

The ocean’s own soundtrack offers a real-time audit of both corporate choices and climate trends. The question is whether humanity will heed that cue before the chorus of the deep becomes a roar no creature can escape.