Deep sea gullies as a gigantic mixing plant

Turbulence releases as much energy as a nuclear power plant

Profiler © Florida State University
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More than 1, 500 meters below the surface of the Atlantic Ocean, halfway between New York and Portugal, there is a gigantic mixing plant: huge volumes of water rush between the narrow gorges of a submarine mountain and form the strongest turbulences ever discovered in the deep sea. They could even play a crucial role in the global system of the sea and the climate, as researchers now report in "Nature".

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Researchers from the US and France discovered the turbulence when they explored the Mid-Atlantic Ridge near the Azores during a three-week expedition with a French research vessel. The undersea mountain range stretches like a seam from north to south through the Atlantic and marks the boundary of the tectonic plates that meet here. It has long been known that this mountain ridge also affects the ocean currents, but how strong the turbulence really is here and what role they play could only now be clarified.

Amount of energy of a nuclear power plant

Scientists are using a specially developed instrument, the "Turbulence Profiler", to measure the turbulence generated by the gushes and passes of the undersea mountains. "The turbulence profiler outputs the amount of energy as watts, the same unit that is on our bulbs, " said Louis St. Laurent of Florida State University. "In the undersea mountain pass we first measured, we found turbulence levels of one-tenth of a watts per cubic meter of seawater. That's a tremendous amount, if you add up all the seawater in the passage. "In fact, the researchers then come to the amount of five million watts - comparable to the amount of energy that produces a nuclear power plant.

Crucial for temperature balance of the Atlantic

At the same time, for the first time, the study provided evidence that water turbulence in these deep-sea regions plays a large part in the mixing of warm and cold waters of the Atlantic. ST. Laurent compares the events on the Mid-Atlantic Ridge with the wind whistling on land through gulches: "This wind creates a turbulence that can blow your hat off your head, " says the researcher. "In the sea, this turbulence is created when water flows quickly through the ocean passages. This turbulence mixes the cold water near the seafloor with the warmer water near the surface. "Display

This realization is significant because this blending depends on the total balance of sea temperatures - and it in turn controls ocean currents. The strength of the Gulf Stream, the ocean current that begins in the Gulf of Mexico and brings warm water to the coast of Europe as a "heating", ultimately depends on it.

Impact on the global climate

"Oceanographers are working hard to understand how marine processes contribute to keeping the Earth's climate stable, " explains St. Laurent. We know that the climate is warming, but we still do not fully understand what impact these changes will have on humanity. Our work can help to develop better models that show how the ocean will affect the future climate. The improved models also provide insight into the process of sea-level rise and the effects of weather changes for example, fishing.

(Florida State University, 10.08.2007 - NPO)