Mysterious deep-sea jets alter global climate

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Washington: For the first time, scientists have discovered mysterious deep-seat jets of water which cause anomalies in wind, rainfall and sea temperature across the tropical Atlantic.

Past research has shown that the oceans impact climate in a multitude of ways, most notably with the ocean-atmosphere phenomena known as El Nino and La Nina, where patterns of warmth and cold in the Pacific wreak havoc worldwide.

Now oceanographers found that regular climate fluctuations in the tropical Atlantic are apparently caused by hitherto unknown deep jets of water travelling from the abyss up about 3,000 meters, LiveScience reported.

"To date, when trying to explain tropical climate variations, we have always looked upwards, specifically to the atmosphere," said researcher Peter Brandt of the Leibniz Institute of Marine Sciences in Kiel, Germany.

"Our new data, for the first time, direct our attention towards the depths of the ocean, thereby opening new perspectives."

Detailing their findings in the journal Nature, the researchers said these currents flow at speeds of 1,180 to 2,360 feet per hour (10 to 20 centimetres per second) along the equator, crossing the entire Atlantic.

The kinetic energy they pack alters surface currents, leading to fluctuations in climate that regularly cycle about every 4.5 years

Among the areas these fluctuations impact is West Africa. Rainfall linked with the West African Monsoon has a big effect on agriculture, water resources and health concerns in one of the more densely populated regions in Africa, Brandt said.

The scientists investigated these jets from the abyss using deep-sea moorings located along the equator, consisting of several miles of wire held upright in the water column by floats and buoys.

Instruments mounted along the wire continuously recorded water speed, direction, salt levels and temperature over the long term.

The researchers also gathered data using freely drifting deep-sea buoys called Argo floats, as well as from satellite.

"We have studied sea surface temperature variability in the tropical Atlantic for a long time and we also study deep circulation," Brandt said. "At one point, we saw that they are both closely connected."

It still remains uncertain what might cause these deep jets. But, it is speculated that strong monthly fluctuations in movement of the ocean`s surface propagate downward to generate conditions for the jets in the abyss, Brandt said.

"How large the effect of these deep jets is, and how they are generated is still somewhat of a mystery. We still have a lot of work ahead of us," he said.

He said that they are going to retrieve and redeploy our moorings along the equator on a research cruise this month.

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