Systems thinking and the evolution of an idea

Acoustic Tomography of Ocean Climate

In the early 1990’s Physical Oceanographer Walter Munk was proposing the deployment of a technology called “Acoustic Tomography of Ocean Climate” (ATOC), whereby loud, low frequency sounds would be projected from the Pioneer Seamount across the Pacific Ocean, to Kauai, with the understanding that the distortions of ATOC signals would tell scientists something about the water in between.

In the case of ATOC, the proposal was to measure thermal characteristics of the ocean – and track global warning. But Munk had been talking about using the ocean as a communication channel – an ocean internet, for some time.

When the public caught wind of this, they understandably became alarmed; sounds loud enough to travel thousands of miles need to be really loud, and at the time very little was known about the effects of loud noises on marine life. And while Walter Munk was a brilliant oceanographer, he didn’t seem to have much sympathy for biology.

There were some contentious public hearings with a decided opacity in views between the proponents of the program and the concerned public. This was aggravated by the fact that the proponents had pretty much dismissed the public because “they didn’t understand the science,” and the public was exasperated by Munk’s aforementioned lack of sympathy for marine mammals.

Although I didn’t know it then, this situation was my gateway to a new job description. At the time I was designing technical facilities – specifically recording studios and museum exhibits, integrating the fields of signal processing, electronic design, and acoustics. So while there was no data on the biological impacts of the proposed noise, I had a grasp on the physics of the problem, and was able to describe it to a lay audience (and my eventual evolution towards science communication).

From then on I began attending public hearings and conferences on anything ‘ocean noise’ associated. And while I was only mildly concerned about ATOC, the implications of getting coherent signals across ocean basins alarmed me – because what it implied for US tactical submarine strategies.

Around the same time various global space agencies were launching satellites equipped with very sensitive magnetometers – sensing ferro-magnetic objects from space. Submarines of that era were getting their mission orders by way of very-long-wavelength radio communications. In order to receive these communications, the subs had to get close to the surface and feed out three-kilometer-long floating antennas – antennas which could be easily spotted by the satellites – completely blowing their cover.

Any magnetometer-equipped satellite could track all of the US submarines.

In order to remain hidden, the Navy would need to replace submarine radio communications with acoustical communications – using the ocean as an acoustical communication channel. This would solve the “surreptitious submarine” problem, but it had grave implications in disrupting the acoustical channels used by marine animals.

Parallel to the development, and then the decade roll-out of ATOC, the US Navy was developing their Low Frequency Active Sonar program (LFAS). While the stated purpose of LFAS was the detection of submarines at long distances, the signals could be easily adapted to transmit other information.

Using ATOC to convey mission orders would be something that the Navy would “neither confirm or deny,” but based on the stated use of the technology, we ended up in a few tussles with them about it, including being a plaintiff on a NRDC led case on its use.

Given the ruling on the case, and the way the Navy took it, I suspect that they have devised other ways of contacting their subs. But the use of the ocean for acoustic communication continues to be an environmental threat.