Washington, April 17 : Scientists have confirmed the presence of mysterious striped pattern of currents on every ocean of the planet.
Between 1992 and 2003, Peter Niiler of the Scripps Institution of Oceanography in San Diego, California, and colleagues collected data from more than 10,000 drifting ocean buoys, which they tracked with satellites.
As expected, the buoys' movements were influenced mainly by known global currents, which are driven by wind and by differences in the temperature and salinity of seawater.
But when the team analysed the data, it emerged that something else had been subtly influencing the buoys' paths. It turned out that there were alternating strips of water running eastward or westward, a bit like parallel moving sidewalks.
Satellite measurements showed that the interfaces between adjacent currents were alternately associated with slight peaks and troughs in sea level.
When the team looked at this variation globally, they found that the 150-kilometre-wide bands covered pretty much every ocean.
To confirm that the currents were real, the team set out to measure them directly in two regions in the eastern Pacific.
"Their existence is so surprising that we had to prove first that they are not an artefact of satellite data," said Nikolai Maximenko of the University of Hawaii.
Sure enough, they recorded currents flowing in opposite directions at around 40 metres per hour. This is slower than most previously known ocean currents, which may explain why the striped flows have remained undiscovered until now.
The flows extend right down to the ocean floor, and the boundaries between currents are alternately associated with peaks and troughs in temperature as well as sea level. This suggests that they influence processes such as nutrient and energy flow around the oceans, but this has yet to be proven," said Niiler.