Researchers at MIT have been working on the secret of waves, and more precisely on "internal" waves. That is, the ones we can't see because they are below the water's surface. These detailed field studies, laboratory experiments and simulations of the largest known "internal" waves in the world were recently published in a report and could significantly improve global climate models. These internal waves play a key role in mixing ocean waters and greatly affect ocean temperatures. Now 42 researchers from 25 institutions in five countries know a little more about these invisible waves from birth to death. " What this report presents is a complete cradle-to-grave picture of these waves." says Thomas Peacock, associate professor of mechanical engineering at MIT, and one of the two lead authors of the paper. The paper was published in the journal Nature .
The phenomenon of "internal" waves
The "internal" waves âeuros giant waves under the surface of the water that are a mixture of salt water and clearer water less salty âeuros are ubiquitous in the oceans of the world. But the largest and most powerful are those that form in the South China Sea, coming from the Luzon Strait, between the Philippines and Taiwan. These ground waves can reach 500 m high and generate powerful turbulences. Their immense size and propagation are important to decipher and analyze, because they play a role in the unfolding of marine processes : supply of nutrients for marine organisms, distribution of sediments and pollutants or propagation of sound waves. Internal" waves are also an important factor in the mixing of oceanic waters, combining the warmer surface waters with the cold deep waters. This process is essential to understand the dynamics of global climate.
Understanding the life cycle of "The Hawai Ocean Mixing Experiment. This new study looked at internal waves that were much stronger and went much further, determining how waves are created and how their energy dissipates. One of the unexpected discoveries Peacock explains was the degree of turbulence produced by the birth of the waves that give life to the tides and currents on the ocean floor. " waves
This international research, called IWISE (Internal Waves In Straits Experiment) was something of a rarity in the field, says Peacock. The last such internal wave field experiment was in 2002, " he said, revealing " These are unexpected discoveries in the field."
Understanding the power of " an intense mixture never observed in the depths of the ocean. It's like a giant washing machine. The mixing is much more spectacular than we expected." waves
The new observations resolve a long-standing technical question that is "internal"Are these waves all powerful from the start or do they become powerful as they spread? There have been many attempts at contradictory answers over the years.
To answer this question, mooring lines were positioned on the seabed (3000 m deep), connected to buoys at the surface, with instruments placed at regular intervals on these lines. Thus, the researchers were able to answer this question. Peacock explained " how do internal waves spread their power? " The study also provided evidence that solitary internal waves continued to be present in the South China Sea during the winter months, contrary to the hypothesis.
Better understand underwater activities
Deciphering these internal waves could be useful to researchers in many fields. Waves are the key to certain ecosystems â?" for example, they allow certain marine creatures to move towards the shore, to feed or even to reproduce. In particular, in the South China Sea, this process contributes to maintain a vast system of coral reefs. Waves also contribute to the diffusion of heat from the ocean surface to the deep ocean, an important parameter in climate modeling. These studies are also important to better predict the impacts on human activities and especially for the oil and gas industry in the China Sea.
