Few things have captured public imagination quite like “The Bloop.” This enigmatic sound, first detected over two decades ago, became one of the most famous underwater mysteries. It sparked widespread speculation about its origin.
The Bloop’s Discovery
The Bloop was a powerful, ultra-low-frequency underwater sound. It was initially detected in 1997 by the National Oceanic and Atmospheric Administration (NOAA) using its autonomous hydrophone arrays. These arrays are now crucial for monitoring ocean acoustics and seismic activity.
The sound’s immense amplitude allowed it to be heard on multiple sensors located over 5,000 kilometers (approximately 3,100 miles) apart. This unique acoustic profile, combined with its unknown source, immediately presented a scientific puzzle. It rose rapidly in frequency over about one minute, unlike any previously identified natural or biological sound.
Tracing the Source
The Bloop’s origin was triangulated to a remote point in the South Pacific Ocean, near the Antarctic region. Scientists estimated its source to be around 50°S 100°W. This location, far from human activity, heightened the mystery surrounding the sound.
Pinpointing its exact origin was challenging initially. While hydrophones allowed for a general area to be identified, the sheer scale of the sound’s propagation meant its source could be a significant distance from any single detection point.
The Scientific Explanation
Initial public theories about the Bloop ranged from giant, undiscovered sea creatures to secret military operations due to the sound’s immense power and unique characteristics. However, scientific investigation by NOAA’s Pacific Marine Environmental Laboratory (PMEL) eventually provided a different explanation.
NOAA scientists conducted extensive research, comparing the Bloop’s acoustic signature to various known underwater sounds. They concluded that the Bloop was consistent with the sounds of large icequakes or iceberg calving. These events involve the fracturing and melting of massive icebergs in the Antarctic.
The conclusion was reached because the Bloop’s frequency, amplitude, and spectrographic characteristics closely matched those of known ice-related seismic activity. Icequakes are cryoseisms, seismic events caused by the cracking and breaking of large ice masses, and they produce powerful, low-frequency sounds that can travel vast distances through the ocean. Further hydrophone deployments closer to Antarctica in the early 2000s allowed researchers to record numerous icequakes with spectrograms very similar to the Bloop, confirming the natural, cryoseismic origin of this once-mysterious sound.