The boundary between cold water and warm, the thermocline, has been important to undersea warfare for hundreds of years of man’s history. Now we have found a way to harness that power for constructive purposes. What once cloaked us can now feed us, what once shielded us from death, now brings us life.
— Captain Ulrik Svensgaard, “The Ripple and the Wave”
All water is identical, but not all water is created equal. This is an important feature of large bodies of water, where depending on what depth you are at, you encounter different temperatures. Ever so slightly counterintuitive, water becomes warmer closer to the surface, especially during sunny seasons; cold water is heavier than warm water, and thus trends downwards by virtue of gravity. The result is a heavily stratified body, with the coldest (albeit still unfrozen) water at the bottom, the warmest at the top, and a middling layer in the middle.
The thermocline is a very specific point where heat is exchanged between the warm water above and the colder water below. As with most places where heat is rapidly exchanged between one thing and another, this is a prime spot for energy generation; heat exchange being, in essence, energy in motion. Svensgaard calls it a lifebringer, and Morgan will (in a later chapter) go on to express his enthusiasm about the free energy just sitting there waiting for someone to tap it.
The thermocline is also, as you might imagine, very loud. A submarine hiding on the other side of it will be nigh invisible on sonar, shielded from listening ears by the roaring motion of water. This cuts both ways, as the very same loudness makes it difficult to ascertain where eventual pursuers are. They may or may not be in pursuit, but there is no way to know for sure unless they come down or you come up.
Svansgaard makes reference to this being a military technology now repurposed for civilian application. As readers will probably remember from previous chapters, this is a very common trajectory for technologies to have. As Virilio wrote about at length, these technologies do not completely lose their military origins, but instead contribute to an overall militarization of society, sometimes implied, sometimes overt. What was once used as a strategic feature of submarine warfare now becomes a fixture of civilian power generation. There is, however, nothing preventing these civilian installations to pull double duty as military sensors in search of enemy vessels; seeing as the construction juts out on both sides of the thermocline by design, they are perfectly suited for that specific purpose. Civilian and military applications are never fully disengaged from each other.