January 9, 2014
Ocean Ecosystem Affected By Powerful Internal Waves: Study
Gerard LeBlond for redOrbit.com - Your Universe Online
New research on the ocean’s hidden waves was conducted in a lab and in the South China Sea. According to a January 8 report from MIT news, internal waves can be hundreds of feet tall and produce damaging effects to the climate and the ocean’s ecosystem.
Experiments in laboratories and in the ocean have scientists claiming to have solved the mystery of what causes the largest internal waves in the world. The new findings, coordinated by the Office of Naval Research (ONR) and conducted by researchers from MIT and several other institutions, was published in Geophysical Research Letters.
The shape of the internal waves are similar to surface waves, but the underwater waves and the water surrounding them have a different density due to temperature; the surface water is warmer and saltier then the water below. An invisible layer between the two can be detected with instruments. Waves are produced within this layer that can be very large and travel considerable distances mixing the ocean waters while drawing heat from the atmosphere.
These internal waves have been a challenge to detect and study. But now, Thomas Peacock, an associate professor of mechanical engineering at MIT, has teamed up with several other researchers to employ the largest experiment ever to study these waves.
Peacock says the waves in the Luzon Strait between Taiwan and the Philippines are “the most powerful internal waves discovered thus far in the ocean. These are skyscraper-scale waves.”
Some of these waves have been observed to reach 550 feet and travel very slowly. Peacock says they are “lumbering giants of the ocean.”
By using a topographical model of the seafloor, and placing a 50-foot diameter rotating tank in Grenoble, France, the experimenters revealed that these waves are generated by the entire ridge of the seafloor, not just a localized area.
The last time a major study of underwater waves was conducted, occurred off the coast of Hawaii in 1999. Since then, scientists have developed a greater appreciation of the effect these waves have on the global climate.
Peacock says, “It's an important missing piece of the puzzle in climate modeling. Right now, global climate models are not able to capture these processes. You get a different answer … if you don't account for these waves.”
Using 15 years of data, the team was able to determine that the waves in the Luzon Strait are steady and predictable, as tides flow over the ridges underneath the surface through narrow channels. This can be seen in the satellite data.
“The strong forcing and ridge geometry at Luzon Strait result in some of the strongest internal waves in the world's oceans. They are important for a variety of reasons, including the region's biology, the mixing and turbulence they produce, and marine navigation in the region,” Matthew Alford, a professor of oceanography at University of Washington, who was part of the team, said in a statement.
“[The research] contributed to a massive advance in our understanding of how these waves get generated and dissipated,” he added.