Side Issues to the IUSS Mission - Hopefully of interest
By Bruce Rule - July 6, 2013
In late March 1991, George Miller, a plank-holder at Adak who had then been with ONI for 29 years, and who made some of the most important contributions ever to data processing technologies and the recovery of critically important S&T - as well as OPINTEL – was reviewing PAC data from multiple sites for the usual purpose.
During that process, he noticed multi-site detections of a very high amplitude, low frequency signal that repeatedly ramped up in frequency. When George asked for information on the source, which was initially detected on 13 March, he was told it was the Santa Barbara Channel oil rig.
Not satisfied with that assessment because of both signal characteristics and amplitude, and also because of its similarity to the Bonin Islands Volcanic Center – previously discussed on this site with reference to the loss of the K-129 - George was able to position the source near 54.1S, 140.5W. Detection ranges were as great as 7,000 nm (other sensors were also involved); the source level was measured as 215 dB.
Several years later, at a time when the System was engaged in selling its potential contribution to marine mammal science, I was shown a detection of a blue whale at an unclassified meeting in San Diego. Well, guess what was all over the same gram? - George's old friend at 54S. The sensor was a sonobuoy located 5,000 miles from the 54S source.
If you go http://io9.com/5883622/meet-the-bloop-the-mysterious-sound-from-the-bottom-of-the-pacific-ocean, you will find discussions of the 54S source, described therein as the “Bloop.” (see quoted discussion below) The site also provides what amounts to a low-resolution lofargram with audio at multiples of the original record speed. As discussed below, by 1996 two French researchers had concluded the source was volcanic, five years after George came to the same conclusion.
“This is Upsweep, which was first recorded in August 1991. Unlike most of the other sounds on this list, it can still be heard. While the noise is strongest in the spring and fall, it appears to be getting generally weaker over time. It's located somewhere deep in the South Pacific near Antarctica, located about 2,500 miles due west of the very southern tip of South America. It was initially thought that this sound might be created by fin whales, but in 1996 researchers Emile Okal and Jacques Talandier argued that there wasn't enough variation in the tone for it to be biological - whales wouldn't be able to communicate much if they only used these same tones over and over. They argued that this was some unusual acoustic phenomenon linked to volcanic activity in the region, perhaps the result of seawater and volcanic gas interacting and creating a resonance pattern. Sure enough, a French research vessel found volcanic seamounts in the region, which makes this the most likely explanation.”
Note also that the 54S source was continuous over extremely long periods. There were no breaks as would have been necessary if the source was a whale which would have had to surface to breath.
Years later, I had the unique opportunity to analyze the very close CPA by a Humpback whale to a single hydrophone moored near the surface in 12,500 feet of water in the South Atlantic. The mammal's heart-rate was detected: 2.7 beats per minute while submerged. Years earlier, George has used striation to determine the speed of a Humpback submerged in the Norwegian Sea: three knots.
And finally, analysis of a Humpback's song detected over a 5-6 hour period indicated the cycle was 18 minutes down, then two minutes up to breathe. The "song" signal structure was incredibly intricate and precisely repeatable to the smallest structural detail. Those characteristics suggest the "song" is produced to hydraulic pressure pulses that excite bone structures into resonance, and, as such, it may be possible to "fingerprint" individual whales. One had to see a very high-resolurtion display of the "song" to appreciate the unbelievable detail in the energy.