Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




WATER WORLD
Breaking deep-sea waves reveal mechanism for global ocean mixing
by Hannah Hickey for UW News
Seattle WA (SPX) Sep 13, 2013


The deep-sea waves are 800 feet tall, as high as a skyscraper. Image courtesy Tom Peacock, MIT and Wide Eye Productions.

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.

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.

.


Related Links
University of Washington
Water News - Science, Technology and Politics






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





WATER WORLD
Deep-ocean carbon sinks
Iowa City IA (SPX) Sep 11, 2013
Although microbes that live in the so-called "dark ocean"-below a depth of some 600 feet where light doesn't penetrate-may not absorb enough carbon to curtail global warming, they do absorb considerable amounts of carbon and merit further study. That is one of the findings of a paper published in the International Society of Microbial Ecology (ISME) Journal by Tim Mattes, associate profess ... read more


WATER WORLD
Japan to boost surveys off Fukushima: report

Iranian telegraph operator, first to propose earthquake early warning system

Workshop report explores use of mass collaboration in disaster management

New technique to assess cost issues from major flood damage

WATER WORLD
First laser-like X-ray light from a solid

Space's 'Ferrari' set to fall to Earth

Chinese-built Bolivian satellite tested in space simulator

Indiana Jones meets George Jetson

WATER WORLD
Libya's beleaguered government faces water threat

Hong Kong bans shark fin at official banquets

Climate change will upset vital ocean chemical cycles

Global warming could change strength of El Nino

WATER WORLD
Arctic ice shrinking in volume, too: ESA

New study points finger at climate in mammoth's demise

Penn Study Finds Earlier Peak for Spain's Glaciers

East Antarctic Ice Sheet could be more vulnerable to climate change than previously thought

WATER WORLD
Almost 20 percent of grain in China lost or wasted from field to fork

Indonesian farmers take legal action against president over haze

Overgrazing turning parts of Mongolian Steppe into desert

Certification of aquaculture critical to sustainable seafood production

WATER WORLD
Volcano prompts declaration of emergency in Peru

Floods kill eight in Romania, hundreds evacuated

Flooding kills three in US state of Colorado

Tropical Storm Gabrielle batters Bermuda: forecasters

WATER WORLD
Summit in Colombia promotes cooperation in African diaspora

Nigerian troops kill 10 insurgents after air strike: army

West pressed hard for end to Congo war

Guinea-Bissau rules out amnesty for coup leaders

WATER WORLD
Paleorivers across Sahara may have supported ancient human migration routes

Orangutans plan their future route and communicate it to others

New evidence that orangutans and gorillas can match images based on biological categories

Synthetic speech system puts a dampener on noisy announcements




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement