(Press-News.org) Waves breaking over sandy beaches are captured in countless tourist photos. But enormous waves breaking deep in the ocean are seldom seen, although they play a crucial role in long-term climate cycles.
A University of Washington study for the first time recorded such a wave breaking in a key bottleneck for circulation in the world's largest ocean. The study was published online this month in the journal Geophysical Research Letters.
The deep ocean is thought of as dark, cold and still. While this is mostly true, huge waves form between layers of water of different density. These skyscraper-tall waves transport heat, energy, carbon and nutrients around the globe. Where and how they break is important for the planet's climate.
"Climate models are really sensitive not only to how much turbulence there is in the deep ocean, but to where it is," said lead author Matthew Alford, an oceanographer in the UW Applied Physics Laboratory. He led the expedition to the Samoan Passage, a narrow channel in the South Pacific Ocean that funnels water flowing from Antarctica.
"The primary importance of understanding deep-ocean turbulence is to get the climate models right on long timescales," Alford said.
Dense water in Antarctica sinks to the deep Pacific, where it eventually surges through a 25-mile gap in the submarine landscape northeast of Samoa.
"Basically the entire South Pacific flow is blocked by this huge submarine ridge," Alford said. "The amount of water that's trying to get northward through this gap is just tremendous – 6 million cubic meters of water per second, or about 35 Amazon Rivers."
In the 1990s a major expedition measured these currents through the Samoan Passage. The scientists inferred that a lot of mixing must also happen there, but couldn't measure it.
In the summer of 2012 the UW team embarked on a seven-week cruise to track the 800-foot-high waves that form atop the flow, 3 miles below the ocean's surface. Their measurements show these giant waves do break, producing 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," Alford said. "We found there's loads and loads of turbulence in the Samoan Passage, and detailed measurements show it's due to breaking waves."
It turns out layers of water flowing over two consecutive ridges form a lee wave, like those in air that passes over mountains. These waves become unstable and turbulent, and break. Thus the deepest water, the densest in the world, mixes with upper layers and disappears.
This mixing helps explain why dense, cold water doesn't permanently pool at the bottom of the ocean and instead rises as part of a global conveyor-belt circulation pattern.
The Samoan Passage is important because it mixes so much water, but similar processes happen in other places, Alford said. Better knowledge of deep-ocean mixing could help simulate global currents and place instruments to track any changes.
On a lighter note: Could an intrepid surfer ride these killer deep-sea waves?
"It would be really boring," admitted Alford, who is a surfer. "The waves can take an hour to break, and I think most surfers are not going to wait that long for one wave."
In fact, even making the measurements was painstaking work. Instruments took 1.5 hours to lower to the seafloor, and the ship traveled at only a half knot, slower than a person walking, during the 30-hour casts. New technology let the scientists measure turbulence directly and make measurements from instruments lowered more than 3 miles off the side of the ship.
The researchers left instruments recording long-term measurements. The team will do another 40-day cruise in January to collect those instruments and map currents flowing through various gaps in the intricate channel.
INFORMATION:
Co-authors of the paper are James Girton, Gunnar Voet and John Mickett at the UW Applied Physics Lab; Glenn Carter at the University of Hawaii; and Jody Klymak at the University of Victoria. The research was funded by the National Science Foundation.
For more information, contact Alford at 206-221-3257 or malford@apl.washington.edu. Note: Alford will be traveling Sept. 13-20 and best reached via e-mail.
END
SAN ANTONIO (Sept. 9, 2013) — Research from the School of Medicine at The University of Texas Health Science Center at San Antonio suggests the exciting possibility of using cell transplants to treat schizophrenia.
Cells called "interneurons" inhibit activity within brain regions, but this braking or governing function is impaired in schizophrenia. Consequently, a group of nerve cells called the dopamine system go into overdrive. Different branches of the dopamine system are involved in cognition, movement and emotions.
"Since these cells are not functioning properly, ...
HOUSTON -- (Sept. 9, 2013) -- The next experiment from Rice University's Multi-Robot Systems Laboratory (MRSL) could happen on your desktop. The lab's researchers are refining their control algorithms for robotic swarms based upon data from five free online games that anyone can play.
"What we learn from the game and our lab experiments applies directly to real-world challenges," said Aaron Becker, a postdoctoral researcher at MRSL. "For example, if a doctor had a swarm of several thousand microscopic robots, each carrying a tiny payload of anti-cancer drugs, might it ...
WASHINGTON, DC—Smart as the Mars Curiosity mission has been about landing and finding its own way on a distant world, the rover is pretty brainless when it comes to doing the science that it was sent 567 million kilometers to carry out. That has to change if future rover missions are to make discoveries further out in the solar system, scientists say.
The change has now begun with the development of a new camera that can do more than just take pictures of alien rocks – it also thinks about what the pictures signify so the rover can decide on its own whether to keep exploring ...
A new study has revealed that the stunning iridescent wings of the tropical blue Morpho butterfly could expand the range of innovative technologies. Scientific lessons learnt from these butterflies have already inspired designs of new displays, fabrics and cosmetics.
Now research by the University of Exeter, in collaboration with General Electric (GE) Global Research Centre, University at Albany and Air Force Research Laboratory, and funded by the US Defense Advanced Research Projects Agency (DARPA), has discovered that the physical structure and surface chemistry of ...
TORONTO, Sept. 9, 2013 – Men were more likely to develop a physical illness than women during a 10-year period studied by researchers at St. Michael's Hospital.
Having a mental illness increases the risk of developing a physical illness by 10 times in both men and women, the study found.
However, women with mental illness tend to develop a physical illness a year earlier than men, according to the study by Dr. Flora Matheson, a scientist in hospital's Centre for Research on Inner City Health.
Women were at a 14 per cent reduced risk, compared to men, of developing ...
Irvine, Calif., Sept. 5, 2013 – What can the U.S. military learn from a common squid? A lot about how to hide from enemies, according to researchers at UC Irvine's Henry Samueli School of Engineering.
As detailed in a study published online in Advanced Materials, they have created a biomimetic infrared camouflage coating inspired by Loliginidae, also known as pencil squids or your everyday calamari.
Led by Alon Gorodetsky, an assistant professor of chemical engineering & materials science, the team produced reflectin – a structural protein essential in the squid's ability ...
Studies of a therapy designed to treat amyotrophic lateral sclerosis (ALS) suggest that the treatment dramatically slows onset and progression of the deadly disease, one of the most common neuromuscular disorders in the world. The researchers, led by teams from The Research Institute at Nationwide Children's Hospital and the Ludwig Institute at the University of California, San Diego, found a survival increase of up to 39 percent in animal models with a one-time treatment, a crucial step toward moving the therapy into human clinical trials.
The therapy reduces expression ...
(SACRAMENTO, Calif.) — The degeneration of a small, wishbone-shaped structure deep inside the brain may provide the earliest clues to future cognitive decline, long before healthy older people exhibit clinical symptoms of memory loss or dementia, a study by researchers with the UC Davis Alzheimer's Disease Center has found.
The longitudinal study found that the only discernible brain differences between normal people who later developed cognitive impairment and those who did not were changes in their fornix, an organ that carries messages to and from the hippocampus, ...
Sept. 9, 2013 – Toronto, Canada –
Scientists at the Centre for Addiction and Mental Health (CAMH) and University Health Network (UHN) have found a new link between early-onset Parkinson's disease and a piece of DNA missing from chromosome 22. The findings help shed new light on the molecular changes that lead to Parkinson's disease.
The study appears online today in JAMA Neurology.
Among people aged 35 to 64 who were missing DNA from a specific part of chromosome 22, the research team found a marked increase in the number of cases of Parkinson's disease, compared ...
Some symbiotic bacteria living inside Colorado potato beetles can trick plants into reacting to a microbial attack rather than that of a chewing herbivore, according to a team of Penn State researchers who found that the beetles with bacteria were healthier and grew better.
"For the last couple of decades, my lab has focused on induced defenses in plants," said Gary W. Felton, professor and head of entomology. "We had some clues that oral secretions of beetles suppressed defenses, but no one had followed up on that research."
Seung Ho Chung, graduate student in entomology ...
