Deep sea currents suddenly reversed

Research by a scientific team from England, Germany, France and Italy using computational models and an acoustic Doppler current measuring device (ADCP) mounted on the seabed discovered that deep-sea currents change much more strongly than understood. knew before. Results published in the journal Nature Geoscience.

Dr. Mike Clare, a sedimentologist at the National Oceanography Center, UK and co-author of the study, said: “The system of ocean currents operating across the planet is much more complex than the textbook model suggests. “.

Scientists use acoustic Doppler current measurement (ADCP) sensors mounted on the seabed. Italian oil and gas company Eni has deployed 34 ADCPs over an area of ​​about 2,500 km2² in the Mozambique Channel. The company shares data from equipment that measures flow speed and direction every 10 minutes for four years.

When Lewis Bailey, a geologist at the University of Calgary, analyzed data from the ADCP, the results were so different from the steady northward flow trend that he wondered if he had made a mistake. However, reality shows that seabed currents often speed up, slow down and even reverse. “We were surprised to see how the currents varied even between moorings that were quite close together,” Bailey said.

“All the geologists involved in the project were amazed by this transformation,” says Clare.

Researchers investigating the cause of the variation found that currents change with the seasons and tidal cycles. ADCP and eroded seafloor models show that the flow on the open sea slope is generally northerly. But in underground canyons, currents often reverse, flowing up or down their length. Scientists speculate that tides and seabed topography are the main causes of current characteristics.

Previously, a study by Rutgers University (USA) published in Science magazine also showed that ocean currents play an equally important role in regulating the Earth’s climate.

In the study, scientists say the major cooling of Earth and continental ice in the Northern Hemisphere 2.7 million years ago occurred concurrently with a shift in ocean flow – pulling heat and CO2 in the Atlantic Ocean, moving them across the deep ocean floor from north to south until heat and carbon dioxide are released in the Pacific Ocean.

Scientists believe that the ocean conveyor system (deep ocean currents) changed at the same time as an expansion in the volume of glaciers in the Northern Hemisphere as well as a significant lowering of water levels. sea. It was Antarctic ice, they argued, that cut off heat exchange at the sea surface and pushed it into deep water. They believe this has caused global climate change.

The study demonstrates that variations in heat distribution across ocean basins are important for understanding future climate change.