Researchers have assembled the most detailed picture of ocean currents ever produced, and in so doing they have revealed a vast array of striated currents that roughly parallel the equator. This new level of resolution should improve understanding of a wide variety of ocean-related phenomena.
Scientists have had a relatively easy time deciphering the big movements in the oceans. Major currents such as the Gulf Stream are easy to detect, for example, and climate researchers for some time have been tracking the Global Conveyor Belt--a giant underwater river that carries cold Arctic waters from the North Atlantic to the middle of the Pacific. More subtle ocean dynamics, known as weak structures, have remained largely invisible. Now an international team has assembled a high-resolution picture of the oceans using satellite radar and 20 years' worth of data collected from thousands of sensors in an ocean-surface network called the Global Drifter Program.
One of the most dramatic features revealed by the new data is a network of banded currents moving west to east and vice versa across all of the oceans at the snail's pace of about 30 meters an hour. "They're almost everywhere," says physical oceanographer and co-author Peter Niiler of the Scripps Institution of Oceanography in San Diego, California. "We've discovered many more weak structures than we thought," Niiler says. As Niiler, lead author Nikolai Maximenko of the University of Hawaii, Honolulu, and colleagues reported 24 April in Geophysical Research Letters, the currents in the northeastern Pacific, which move back and forth from the U.S. West Coast to Hawaii, could be the source of an important current that loops up the California coast and back south.
"Who would have thought the bands would be so ubiquitous," says geophysical fluid dynamicist Geoff Vallis of Princeton University. And physical oceanographer Terrence Joyce of Woods Hole Oceanographic Institution in Massachusetts says the currents "may well represent something completely different" from the usual products of temperature and other ocean dynamics. "Their physical cause is obscure," he says.