Communication signals threaten marine habitat

Commnuication and navigation beacons.

Back in the mid 1970’s Physical Oceanographer Walter Munk was evaluating the acoustical transmission characteristics of the ocean “sound channel” – an isothermal layer in the deep ocean that baleen whales use for long distance communication.

His visionary work in this field developed into a 1991 experiment called the “Heard Island Feasibility Test” which produced the first sound that was literally heard around the world – under water.

The utility of this ocean feature for long distance communication was something Dr. Munk had been advancing ever since 1978 when he proposed a “Sea Net” – an acoustic based ocean internet system that could be used – and heard around the world.

It was along this trajectory that the “Acoustic Thermography of Ocean Climates” (ATOC) was proposed, and then deployed in 1992 despite the misgivings many of us had about projecting very loud sounds throughout the entire Pacific Basin.

ATOC turned out to be relatively benign, but for me it was the harbinger of things to come; where all manner of acoustic signals would be used for research, military, and industrial communication –crowding out the important bio-acoustic signals of marine animals.

The signals and technologies continued to develop, and it was in 2000 with a US Navy proposal of a long distance sonar system called “SURTASS” (which would ensonify the entire ocean with military noise) that the public became aware of the problem.

Public hearings were conducted, lawsuits filed, and demonstrations ensued. It was in the midst of this gambit that the Bahamas Stranding occurred – alerting us all that despite the assurances of our Navy that there was indeed a problem.

It is the continuous association between military operations and marine mammal strandings that has kept the Ocean Noise Pollution issue in the public conversation. While most of this conversation orbits around military sonar and seismic surveys, the exponential advance of other acoustical communication and navigation signals threatens to seriously compromise the marine bio-acoustic habitat.

This link describes one such signal, but there are many others being developed and deployed for research, industrial, and military applications.

While some of these signals may not be pernicious – even while overlapping some odontocete communication and bio-sonar bands, it would be good to know this prior to saturating biologically significant habitat with sounds generated by expensive equipment.

Tools to make this determination is one of OCR’s banner projects which we hope to complete this year pending support from funding agencies.

When we do complete these tools it will be none too soon, as underwater communication systems are springing up like mushrooms all over the sea.

Stay tuned!

Lunar connection on Hanalei Bay stranding nixed.

Hanalei Bay Melon headsOn the morning of July 3 2004 there was an agitated aggregation of Melon Headed whales in Hanalei Bay, Hawai’i. This event was concurrent to the RIMPAC international naval exercise  which happens every two years.

As is typical with these tragic events, the US Navy rolled up their collective sleeves and focused on how to establish that they were not responsible.

In this case they started out with the claim that the exercises were not in progress until after the event. They also sponsored an extensive modeling of the event and presented the findings at the Fall 2004 Acoustics Society meeting. (“Analysis of melon-headed whale aggregation in Hanalei Bay,” David Fromm et. al JASA 2004)

While Dr. Fromm’s presentation was interesting, it was also fraught with data gaps – such as an analysis of the frequencies and signal types used in the exercises. The study also reiterated their claim that the “embayment” happened before the Navy commenced the exercise (which was later in the day than the stranding.).

A critical element that was omitted from the study was that the warships were calibrating their sonar prior to commencing the exercises. These calibrations were coincident to the embayment of the whales.

There were a number of other troubling  assumptions that did not square with the incident – including a “lunar” connection (based on an aggregation of melon headed whales that occurred on the same day in Japan). All tolled, it was a well funded, beautifully presented model based on exculpating assumptions – and ultimately signifying very little. The paper has not been published after peer review, and remains in abstract form in the J. Acoustical Society of America.

Hallway comments from closely linked (Office of Naval Research- ONR) sponsored scientists seemed to agree that the modeling was an expensive “CYA” presentation (their words).   Your tax dollars at work…

Noise impacts from military communication sonars are much more widespread than the US Navy would like to admit. ONR is funding research on the impacts,  but their priorities seem more focused on how to prevent these embarrassing stranding events from occurring – such as spatial-temporal planning and “recoverable threshold” testing on marine mammals – rather than  determining what the mechanism is for the aggravation.

We believe that the Navy could accomplish their mission safely if they chose to examine the signal characteristics that are agonistic and then crafted communication signals that are more benign.

Toward this end we are working on a metrics system that can qualify noise by loudness as well as “roughness” – the characteristic that distinguishes the differences between alarming sounds and pleasant sounds that may be equally loud. Hopefully this ‘metric’ will provide design guidance in the tempering of mid-frequency communication sonar signals.

The referring article is in AAAS Science with a nice title “Whale Stranding: Sonar or Lunar

Cornwall Mass Stranding Event

Cornwall Stranding

The mass stranding event (MSE) in Cornwall UK last year points to Navy sonar. But if you read through the very comprehensive report you can see why it is difficult to arrive at unimpeachable scientific conclusions.

The report is here:

The quote from the report conclusion states:

“A period of naval exercises involving a variety of high intensity acoustic sources were conducted around the time of the MSE, but evidence of one of more specific naval activities that tightly coincided in time and space with the likely initial onset of the MSE were absent in all the records of naval activities released under the Freedom of Information Act.”

The term “tightly coincided in time” is at issue because the exercises were conducted within 60 hours of the strandings – close enough to not be eliminated as a cause, but not so close as to indicate sonar as a definitive reason for the stranding.

The report is quite thorough and illustrates why it is so difficult to ascertain causation for any stranding event.

This illustrates why the US Navy can state with scientific certainty that “only 37 whales have stranded as a consequence of Navy sonar.”

In science there is no Racketeer Influenced and Corrupt Organizations (RICO) act that can indict criminals because they always seem to be around the scene of a crime. We can only look at the correlations and make our informed assumptions.

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