Detailed new field studies, laboratory experiments, and simulations of the largest known “internal waves” in the Earth’s oceans — phenomena that play a key role in mixing ocean waters, greatly affecting ocean temperatures — provide a comprehensive new view of how these colossal, invisible waves are born, spread, and die off.

The work, published today in the journal Nature, could add significantly to the improvement of global climate models, the researchers say. The paper is co-authored by 42 researchers from 25 institutions in five countries.

“What this report presents is a complete picture, a cradle-to-grave picture of these waves,” says Thomas Peacock, an associate professor of mechanical engineering at MIT, and one of the paper’s two lead authors.

Internal waves — giant waves, below the surface, that roil stratified layers of heavier, saltier water and lighter, less-salty water — are ubiquitous throughout the world’s oceans. But by far the largest and most powerful known internal waves are those that form in one area of the South China Sea, originating from the Luzon Strait between the Philippines and Taiwan.

These subsurface waves can tower more than 500 meters high, and generate powerful turbulence. Because of their size and behavior, the rise and spread of these waves are important for marine processes, including the supply of nutrients for marine organisms; the distribution of sediments and pollutants; and the propagation of sound waves. They are also a significant factor in the mixing of ocean waters, combining warmer surface waters with cold, deep waters — a process that is essential to understanding the dynamics of global climate.

This international research effort, called IWISE (Internal Waves In Straits Experiment), was a rare undertaking in this field, Peacock says; the last such field study on internal waves on this scale, the Hawaii Ocean Mixing Experiment, concluded in 2002. The new study looked at internal waves that were much stronger, and went significantly further in determining not just how the waves originated, but how their energy dissipated.

One unexpected finding, Peacock says, was the degree of turbulence produced as the waves originate, as tides and currents pass over ridges on the seafloor. “These were unexpected field discoveries,” he says, revealing “some of the most intense mixing ever observed in the deep ocean. It’s like a giant washing machine — the mixing is much more dramatic than we ever expected.”

The new observations, Peacock says, resolve a longstanding technical question about how internal waves propagate — whether the towering waves start out full strength at their point of origin, or whether they continue to build as they spread from that site. Many attempts to answer this question have produced contradictory results over the years.