Skip to comments.Invisible waves shape continental slope (climate related)
Posted on 06/30/2008 11:51:20 AM PDT by decimon
AUSTIN, TexasA class of powerful, invisible waves hidden beneath the surface of the ocean can shape the underwater edges of continents and contribute to ocean mixing and climate, researchers from The University of Texas at Austin have found.
The scientists simulated ocean conditions in a laboratory aquarium and found that "internal waves" generate intense currents when traveling at the same angle as that of the continental slope. The continental slope is the region where the relatively shallow continental shelf slants down to meet the deep ocean floor.
They suspect that these intense currents, called boundary flows, lift sediments as the waves push into the continental slope, maintaining the angle of the slope through erosion. The action of the internal waves could also mix layers of colder and warmer water.
"Surprisingly little is known about how internal waves are generated and how they could lead to the mixing of the deep ocean, but it's very important," said physicist Hepeng Zhang. "Understanding ocean mixing is crucial for us to know whether changes in ocean circulation are the result of climate change or just variability."
Zhang said that as long as there is tidal motion that generates internal waves traveling along the continental slope, intense boundary flow will be produced.
"Twenty-four hours a day, seven days a week over a long geological time scale, and this will maintain the angle of the continental slope," he said.
He published his research with colleagues Harry Swinney and Benjamin King in Physical Review Letters.
Zhang studied internal waves using a simple saltwater aquarium equipped with a sloping bottom simulating the continental slope. Water in the tank increased in density from top to bottom, just as water is denser on the ocean floor. Thousands of very small particles, 10 microns or smaller, were suspended in the water.
As Zhang generated waves in the tank, he took photographs and video footage of the particles and then analyzed the particles' direction of flow and velocity.
Particle motion revealed intense boundary flows when the angle of the bottom matched the angle at which internal waves can travel.
Oceanic continental slopes could theoretically reach angles of 15 to 20 degrees as sediments continually pour down from the continents, but Zhang said that the internal waves are limiting the angle to around three degrees, the average angle of continental slopes.
The internal waves could also play a role in larger ocean currents by bringing cold water up from the deep ocean to the surface at the equator.
Ocean currents form closed loops, with warm surface water, like the Gulf Stream, moving toward the poles and cold water circulating back toward the equator at depth. The warm surface water heated at the equator is largely driven to the poles by wind. At the poles, this water is cooled by the cold air and mixes with cold water from melting glaciers and ice. Although fresh water is less dense than sea water, the cooling effect wins out and the density increases until the water sinks.
Zhang found that the internal waves could help bring this cold water closer to the surface when the boundary flow pushes heavier, colder water over warmer lighter water on the continental slope. This results in the internal wave breaking and mixing on the slope, just as a surface wave breaks on the shore.
"How exactly this will contribute to ocean circulation, I really don't know," said Zhang. "But it is definitely a step we have to understand before we can understand global ocean circulation."
Editor's Note: Video footage of the internal wave lab simulations are available by contacting Hepeng Zhang or Lee Clippard or the Web site: http://netserver.aip.org/cgi-bin/epaps?ID=E-PRLTAO-101-034852
Don’t tell me, let me guess:
Next it will be announced that global warming (pardon me, “global climate chnage”) is adversely affecting these invisible wave patterns, right?
Sounds similar to the internal waves under HRC’s pantsuit - it looked like two dogs fighting under a blanket.
New discoveries of unknown forces continue to come, yet somehow the climate models predictions are of course not to be questioned.
Two angry bulldogs in a sack.
I'm all for researching climate as humans will eventually have to cope or perish with much warmer or cooler temperatures than we have today. But not enough is presently known to know where we are in the warming-cooling cycle.
"I was following a large woman wearing them britches," Grand pappy said, "and the action there reminded me of two pigs fighting in a totesack."
The Prof wouldn't make it these days.
Here they are:
How did you get that picture?
Wait... It’s a picture of Obama without the suit!
Or... It’s McCain’s knowledge of economics!
Or... It’s everything I’ll have left after a carbon cap & trade system!
Or... It’s the conservatives left in California after 2010!
Or... It’s Michelle’s love of country!
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Turns out it's really Pigs In A Pants Suit
I’ve seen those before, with captions; they were labeled “a” and “b”.
That’s where that expression, “cube b, or not cube b” originated.
Okay, so, it wasn’t worth the setup...
To “b” or not cube “b”...however, cube “a” seems to have frozen rather suddenly...?
My imaginary friends and I are going to surf the invisible waves.
It seems that Zheng is talking about the mixing of different densities of water under the surface. Kinda like the wave in a bottle using oil and water. Cold water may well up and then "crash" wave-like over some warm water in its way causing mixing and scrubbing the continental shelf, then generally returning to its level much like the wave in the bottle. And this goes on night and day, year in and year out.
Isn't this more a study of currents and temperature differentiation than "invisible waves" discussion? I think currents affect IW not the other way around.
If an invisible wave crashes under the surface does anyone hear it.
That image has also been described as "two pigs in a poke".
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