Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Study Finds Surprising New Pathway for North Atlantic Circulation

Oceanographers have long known that the 20-year-old paradigm for describing the global ocean circulation– called the Great Ocean Conveyor – was an oversimplification. It’s a useful depiction, but it’s like describing Beethoven’s Fifth Symphony as a catchy tune.

The conveyor belt paradigm says the Gulf Stream-warmed ocean releases heat to the atmosphere in the northern North Atlantic, leaving ocean water colder and denser as it moves north.

The cold waters sink and flow southward along the “deep western boundary current” that hugs the continental slope from Canada to the equator. To replace the down-flowing water, warm surface waters from the tropics are pulled northward along the conveyor’s upper limb.

But while the conveyor belt paradigm establishes the melody, the subtleties and intricacies of the symphony of global ocean circulation largely remain a puzzle.

Now, research led by oceanographers at Woods Hole Oceanographic Institution (WHOI) and Duke University have teased out a new piece of that puzzle, expanding our understanding of this circulation model. Using field observations and computer models, the study shows that much of the southward flow of cold water from the Labrador Sea moves not along the deep western boundary current, but along a previously unknown path in the interior of the North Atlantic.

The study by co-principal authors Amy Bower, a senior scientist in the WHOI Department of Physical Oceanography, and Susan Lozier, a professor of physical oceanography at Duke University’s Nicholas School of the Environment, will be published in the May 14 issue of the research journal Nature.

“This new path is not constrained by the continental shelf. It’s more diffuse,” said Bower. “It’s a swath in the wide-open, turbulent interior of the North Atlantic and much more difficult to access and study.”

And since this cold southward-flowing water is thought to influence and perhaps moderate human-caused climate change, this finding may impact the work of global warming forecasters.

"This finding means it is going to be more difficult to measure climate signals in the deep ocean," Lozier said. "We thought we could just measure them in the Deep Western Boundary Current, but we really can't."

Lozier and Bower first conceived of this program eight years ago. Studies led by Lozier and other researchers had previously suggested cold northern waters might follow such “interior pathways” rather than the conveyor belt in route to subtropical regions of the North Atlantic.

But testing the idea meant developing an elaborate WHOI-led field program involving the launching of 76 special Range and Fixing of Sound (RAFOS) floats into the current south of the Labrador Sea between 2003 to 2006. The ambitious program would have been prohibitively expensive had it not been for a collaboration with Eugene Colbourne of the Northwest Atlantic Fisheries Center in St. Johns, Newfoundland. Colbourne regularly conducts hydrographic surveys around the Grand Banks, and agreed to deploy the team’s RAFOS floats in groups of six every three months for three years.

Bower worked with a team at WHOI to build the floats and develop the plan for their deployment.

The RAFOS floats were configured to submerge at 700 or 1,500 meters depth – within the layer of the ocean where one constituent of the cold southward-flowing water, called Labrador Sea Water, travels. They drifted with the currents for two years, recording location information as well as temperature and pressure measurements once a day. After two years, the floats returned to the surface and transmitted all their data through the ARGOS satellite-based data retrieval system and were downloaded to scientists in the lab.

To communicate with the floats and to track their position, the team deployed anchored low-amplitude sound beacons in the general area of the experiment, which were set to “ping” automatically every day. The RAFOS floats’s onboard hydrophones detect the sound from the beacons, enabling scientists to determine the distance from the float to the beacon, based on the time delay between when the ping went off and when it was detected.

But only 8 percent of the RAFOS floats followed the conveyor belt of the Deep Western Boundary Current (DWBC), according to the Nature report. About 75 percent of them “escaped” that coast-hugging deep underwater pathway and instead drifted into the open ocean before they get around the Grand Banks. Eight percent “is a remarkably low number in light of the expectation that the DWBC is the dominant pathway for Labrador Sea Water,” the researchers wrote.

Since the RAFOS float paths could only be tracked for two years, Lozier, her graduate student Stefan Gary, and German oceanographer Claus Boning also used a modeling program to simulate the launch and dispersal of more than 7,000 virtual “e-floats” from the same starting point.

Subjecting those e-floats to the same underwater dynamics as the real ones, the researchers then traced where they moved. “The spread of the model and the RAFOS float trajectories after two years is very similar,” they reported.

"The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC, contrary to previous thinking," their report concluded.

Next, Bower and Lozier hope to extend their research to study the southward flow of cold water originating even farther north in the Greenland Sea.

This research was supported by the National Science Foundation.

The Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment.

WHOI Media Relations | Newswise Science News
Further information:

More articles from Earth Sciences:

nachricht Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ

nachricht New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Space observation with radar to secure Germany's space infrastructure

Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.

The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

New solar solutions for sustainable buildings and cities

23.03.2018 | Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

Latest News

For graphite pellets, just add elbow grease

23.03.2018 | Materials Sciences

Unique communication strategy discovered in stem cell pathway controlling plant growth

23.03.2018 | Agricultural and Forestry Science

Sharpening the X-ray view of the nanocosm

23.03.2018 | Physics and Astronomy

Science & Research
Overview of more VideoLinks >>>