Tuesday, April 22, 2008

Ocean is striped with opposing currents--now, to find them...

Outrigger canoe steersmen look for the currents flowing the way they're going, which often can be only a few yards from flows that work against them.

Open ocean sailors can describe the oceanic furor where a major east-flowing current slides alongside a west-flowing section.

Scientists, including ones at the University of Hawai'i, have now determined that these changes in direction are amazingly common in the ocean. They are referring to the “striped” currents that are superimposed on every ocean.

In an article printed in New Scientist, researchers describe being shocked to discover the zebra quality of the oceans. A team led by Peter Niiler, of Scripps Institute of Oceanography studied the data from more 10,000 buoys drifting on the open oceans, and whose movements are tracked by satellite.

Clearly, the researchers found, the drifting buoys were being pushed by the wind, and were reacting the known major currents. But there was something else going on as well.

They were finding that buoys appeared to be responding to side-by-side flows in opposite directions. And where these currents met, there were either troughs or peaks in sea level. The current sections were about 90 miles wide, and existed all over the ocean.

“My god, we've never seen these before,” Niiler said in the New Scientist article.

The implications of the findings are significant, although the article didn't go into some of them. Although the water movement is comparatively slow, if such current flows are identifiable and predictable, for example, they could be used by oceanic shipping to reduce travel times as well as fuel consumption.

The researchers went out into the eastern Pacific to see whether they could actually detect on the water what they were seeing in the satellite data.

University of Hawai'i oceanographer Nikolai Maximenko, an associate researcher with the International Pacific Research Center, was among those who went out to check on the currents.

“Their existence is so surprising that we had to prove first that they are not an artefact of satellite data,” Maximenko said.

They found the currents. They were just oozing along, at about 120 feet per hour. Barely enough to notice, which may be why nobody noticed them before, he said.

“Only a very lazy canoeist would notice the effect,” Maximenko said.

On the other hand, the difference between going with the flow and going against it is 240 feet an hour, and in a four-hour boat race, being in the right flow could make a 1,000-foot difference at the finish. More than enough to make the difference.

The flows appear to extend deep into the ocean, and they could play a role in moving nutrients and ocean temperatures around. But researchers still don't know why they're there.

“They are a fascinating new aspect to the ocean's circulation, but the jury is still out on the mechanisms leading to their formation,” said Princeton University researcher Geoff Vallis.

© 2008 Jan W. TenBruggencate