Folks who have been on the internet for a while are probably familiar with the Bloop, an “ultra-low frequency and extremely powerful underwater sound detected by the U.S. National Oceanic and Atmospheric Administration (NOAA) in 1997.” It’s been the source of some puzzlement and speculation and OMG IT’S CTHULHU!!!
Anyway, via Doubtful News, the VENTS program at NOAA is venturing an opinion, both to the nature of the sound and probably location from which it originated:
The broad spectrum sounds recorded in the summer of 1997 are consistent with icequakes generated by large icebergs as they crack and fracture. NOAA hydrophones deployed in the Scotia Sea detected numerous icequakes with spectrograms very similar to “Bloop”. The icequakes were used to acoustically track iceberg A53a as it disintegrated near South Georgia Island in early 2008. Icequakes are of sufficient amplitude to be detected on multiple sensors at a range of over 5000 km. Based on the arrival azimuth, the iceberg(s) generating “Bloop” most likely were between Bransfield Straits and the Ross Sea, or possibly at Cape Adare, a well know source of cryogenic signals.
I don’t know if you can really solve a question like this, maybe the deep ones just sound a lot like icequakes, but I think this should put a damper on some of the sillier speculation.