Scientists Finally Know What's Causing the ‘Bloop’ Sound in the Southern Pacific Ocean
Deep within the Southern Pacific waters, the eerie silence is interrupted by some strange, elusive sounds that travel through the body of the ocean. In 2002, oceanographer Christopher Fox was staring at his computer screen that flashed and played sounds with strange names like Train, Whistle, Slowdown, Upsweep, and Bloop. There was even one with the name Gregorian Chant. While most of these sounds have remained evasive, the mystery of the one named “Bloop” has been solved. The ultra-low-frequency sound is one of the loudest echoes rumbling through the belly of Earth’s waters.
Ever since it became trapped in the sound stations sitting on the seabed, the mysterious sound spurred bizarre theories. But as NOAA revealed in a press release, the sound is just a breaking iceberg. With 95% of the oceans remaining unexplored, the chorus of weird sounds rolling in the dark depths evokes a sense of surreal fantasy. When the underwater microphones installed in the Southern Pacific waters by NOAA scientists first captured the Bloop, their brains whipped up a whole database of theories and stories as to what it could be and where it could be coming from. They had been exploring the activities of underwater volcanoes and earthquakes, and suddenly stumbling upon this sound joggled their minds in an eager curiosity.
Was it a sea monster growling or a glowing fish emitting electric pulses? The fact that the sound was undulating in frequency made it even more interesting to the researchers. The more they contemplated it, the more puzzled they became. "Just when you think there're no mysteries left in this world, we have a whole bucket of them on the screen here," Fox shared with New Scientist in 2002. After years and years of waiting and brooding over the mystery, Fox and his fellow scientists at NOAA concluded what they had expected all along. After zillions of attempts to trace the source of this mysterious Bloop, the trail of clues finally led them to the Earth’s lonely southernmost land mass in 2005.
The sound was emanating from aniceberg cracking and breaking away from an Antarctic glacier, a phenomenon known to scientists as “calving.” Their main ally in detecting the sound’s source remained an array of old hydrophones, or underwater microphones initially set up by the US Navy in the 1960s to track Soviet submarines using a system called Sound Surveillance System (SOSUS). This system traps the sounds reverberating through the swirling waters of the ocean and stores them as voice or sonic prints. Back in the laboratory, scientists fetch these prints and analyze the data to conclude the possible sources of the sound being investigated.
When the NOAA studded the Southern Pacific seabed with tons of these hydrophones, they received numerous instances of the “Bloop” sound. Curious and eager to discover its source, scientists from NOAA’s Pacific Marine Environmental Laboratory (PMEL) brainstormed possibilities like a secret underwater military base, ship engines, a fishing boat, some giant squid, a whale song, or some undiscovered sea creature. The observations collected from Antarctica between 2005 and 2010 revealed that the source was simply a crumbling iceberg. The mystery was solved when PMEL researchers took their acoustic survey to an area around Antarctica’s sinister Drake Passage.
There, they discovered that a notorious iceberg was sending this “bloop” running through the ocean currents as it disintegrated, broke apart, and collapsed, provoked by the fury of global warming. Scientists believe that this heating up of the planet, or climate change, is one of the major culprits behind calving icebergs. As more and more icebergs continue to crumple and flake out, it sounds like Bloop might become even more common with the coming days, and so might the treacherous icequakes.
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