New theory of deep-ocean sound waves may aid tsunami detection
Acoustic-gravity waves are very long sound waves that cut through the deep ocean at the speed of sound. These lightning-quick currents can sweep up water, nutrients, salts, and any other particles in their wake, at any water depth. They are typically triggered by violent events in the ocean, including underwater earthquakes, explosions, landslides, and even meteorites, and they carry information about these events around the world in a matter of minutes. Researchers at MIT have now identified a less dramatic though far more pervasive source of acoustic-gravity waves: surface ocean waves, such as those that can be seen from a beach or the deck of a boat. These waves, known as surface-gravity waves, do not travel nearly as fast, far, or deep as acoustic-gravity waves, yet under the right conditions, they can generate the powerful, fast-moving, and low-frequency sound waves. The researchers have developed a general theory that connects gravity waves and...