Monstrous 800-Foot Waves Key to Ocean Circulation

Waves don't only break on beaches. They can also be found deep below the surface of the ocean--enormous monstrosities that drive long-term climate cycles. Now, scientists have learned a little bit more about these waves, revealing that the 800-foot-tall waves are key for ocean circulation.

Huge waves form between layers of water of different density in the deep ocean. These skyscraper-tall waves transport heat, energy carbon and nutrients around the globe. Where exactly they break is important for Earth's climate since they can drastically impact ocean health and temperatures.

"Climate models are really sensitive not only to how much turbulence there is in the deep ocean, but to where it is," said Matthew Alford, one of the researchers, in a news release. "The primary importance of understanding deep-ocean turbulence is to get the climate models right on long timescales."

In order to better understand these deep waves and this ocean mixing, the researchers embarked on a seven-week cruise to track the 800-foot-high waves that form atop a flow that occurs through the Samoan Passage in the South Pacific. They found that these giant waves break and produce mixing 1,000 to 10,000 times that of the surrounding slow-moving water.

"Oceanographers used to talk about the so-called 'dark mixing' problem, where they knew that there should be a certain amount of turbulence in the deep ocean, and yet every time they made a measurement they observed a tenth of that," said Alford. "We found there's loads and loads of turbulence in the Samoan Passage, and detailed measurements show it's due to breaking waves."

Layers of water flow over two consecutive ridges to form a lee wave, like those in air that passes over mountains. These waves eventually become unstable and turbulent and finally break. This causes the deepest and densest water in the world to mix with upper layers.

The findings reveal a little bit more about how these deep sea waves can impact our world. In addition, this same process probably happens in other locations in the ocean. Better knowledge of this deep sea mixing could help simulate global currents and place instruments to track any changes.

The findings are published in the journal Geophysical Research Letters.