The ocean’s vast and unexplored depths hold many secrets, occasionally releasing sounds that defy immediate explanation. These enigmatic acoustic phenomena capture the imagination, prompting both scientific inquiry and public speculation. Among these mysterious underwater noises, one stood out for its sheer power and intrigue: the sound known as the Bloop. This unique acoustic event, detected far beneath the waves, became a significant puzzle, drawing attention to the ocean’s hidden soundscape.
The Bloop’s Discovery
The Bloop was first recorded in 1997 by the U.S. National Oceanic and Atmospheric Administration (NOAA). This ultra-low frequency, high amplitude underwater sound was unlike anything researchers had encountered. It exhibited an undulating profile, rising in frequency over approximately one minute, a characteristic that initially puzzled scientists.
The sound’s source was triangulated to a remote area of the South Pacific Ocean, specifically around 50°S 100°W, west of the southern tip of South America and off the coast of Chile. Detection occurred through the Equatorial Pacific Ocean autonomous hydrophone array, operated by NOAA’s Pacific Marine Environmental Laboratory (PMEL). This array picked up the Bloop on multiple sensors over 5,000 kilometers (3,000 miles) apart, indicating its immense amplitude.
Early Theories and Public Fascination
The Bloop’s unusual characteristics immediately sparked numerous hypotheses among scientists and the public. Given its organic-sounding nature and immense volume, some speculated about an unknown, massive deep-ocean creature. This idea was fueled by the sound’s amplitude, which far exceeded the capabilities of any known animal, including the blue whale.
Other theories proposed conventional sources, such as military exercises, ship engines, or geological activity like volcanic eruptions. The Bloop’s mystery, combined with its seemingly biological signature, captured public imagination, leading to widespread discussion and connections to fictional sea monsters.
Unraveling the Mystery
The scientific investigation into the Bloop’s origin involved data analysis and comparative acoustics. Researchers at NOAA’s Pacific Marine Environmental Laboratory (PMEL) collected and analyzed acoustic data from their hydrophone arrays. This effort included deploying new arrays, particularly closer to Antarctica, to gather more information about natural ocean sounds.
Between 2005 and 2010, these expanded acoustic surveys yielded significant insights. Scientists compared the Bloop’s spectrogram, a visual representation of sound frequencies over time, with recordings of known underwater phenomena. This analysis revealed the Bloop signal’s characteristics were strikingly similar to sounds produced by ice-related events. The true source was identified around 2005, with subsequent tracking of large icebergs confirming the findings.
The Cryoseism Explanation
The definitive scientific explanation for the Bloop is that it was the sound of a large icequake, also known as a cryoseism. A cryoseism occurs from the sudden fracturing of large icebergs or glaciers, resulting from immense stress released as the ice cracks.
Icequakes generate seismic vibrations and loud booming sounds. Their acoustic profiles, including ultra-low frequency, closely match the Bloop. These events are powerful enough for their sounds to travel thousands of kilometers across the ocean, consistent with the Bloop’s widespread detection. Such icebergs are often located in areas like the Bransfield Strait, the Ross Sea, or Cape Adare, regions known for significant ice activity. This natural process, akin to rolling thunder, is common in polar regions, and its frequency is increasing due to climate change.