The Great Ocean Conveyor Belt – blue = deep cold and saltier water current, red = shallower and warmer current
[credit: NWS / NOAA]
Researchers put forward the idea that the role of the global ocean conveyor belt may be overrated in the grand scheme of ocean dynamics, and offer alternative ideas.
Far from the vast, fixed bodies of water oceanographers thought they were a century ago, oceans today are known to be interconnected, highly influential agents in Earth’s climate system, says Phys.org.
A major turning point in our understanding of ocean circulation came in the early 1980s, when research began to indicate that water flowed between remote regions, a concept later termed the “great ocean conveyor belt.”
The theory holds that warm, shallow water from the South Pacific flows to the Indian and Atlantic oceans, where, upon encountering frigid Arctic water, it cools and sinks to great depth.
This cold water then cycles back to the Pacific, where it reheats and rises to the surface, beginning the cycle again.
This migration of water has long been thought to play a vital role in circulating warm water, and thus heat, around the globe. Without it, estimates put the average winter temperatures in Europe several degrees cooler.
However, recent research indicates that these global-scale seawater pathways may play less of a role in Earth’s heat budget than traditionally thought. Instead, one region may be doing most of the heavy lifting.
A paper published in April in Nature Geoscience by Gael Forget, a research scientist in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and a member of the Program in Atmospheres, Oceans,and Climate, and David Ferreira, an associate professor in the Department of Meteorology at the University of Reading (and former EAPS postdoc), found that global ocean heat transport is dominated by heat export from the tropical Pacific.
Using a state-of-the-art ocean circulation model with nearly complete global ocean data sets, the researchers demonstrated the overwhelming predominance of the tropical Pacific in distributing heat across the globe, from the equator to the poles.
In particular, they found the region exports four times as much heat as is imported in the Atlantic and Arctic.
“We are not questioning the fact that there is a lot of water going from one basin into another,” says Forget. “What we’re saying is, the net effect of these flows on heat transport is relatively small. This result indicates that the global conveyor belt may not be the most useful framework in which to understand global ocean heat transport.”
Full article here.
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May 17, 2019 at 04:54AM
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