Scientists uncover surprising new pathway for North Atlantic circulation

May 14th, 2009 - 2:21 pm ICT by ANI  

Washington, May 14 (ANI): A new study has shown 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 was done 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.

“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,” she added.

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.

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.

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 downloaded to scientists in the lab.

Since the RAFOS float paths could only be tracked for two years, Lozier and her team 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 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. (ANI)

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