for National Geographic News
In the recently released movie Riding Giants, big-wave surfers search the globe for the ultimate ride at legendary surf spots such as California's Mavericks. But at unnamed spots in the ocean, there are huge waves that can't be so easily caught.
Known as rogue, or freak, waves, these giants seem to spring up from the ocean floor. They are so large that they can overwhelm and sink even the sturdiest ships.
Now researchers have started using satellites to try to identify and track these unruly waves. And the results have been surprising. While rogue waves were once thought to be the stuff of sailing legend, satellite photos found ten huge waves welling up one three-week period.
"We thought we'd have difficulties finding so many large waves," said Wolfgang Rosenthal, a research scientist at Germany's GKSS research center. "But roughly two ships each week are affected."
Rosenthal and colleagues at GKSS have spent several years looking at 30,000 satellite images of the ocean surface taken by two European Space Agency satellites over a three-week period in 2001.
The satellite images were processed at the Cologne-based German Aerospace Center. This research was part of a European Union program called MaxWave, started in 2000 to document the occurrence of rogue waves.
With this and other studies, researchers want to develop a wave map covering more than a decade of observations of the world's oceans. The map could be used to forecast the likelihood of the giant waves' appearance.
While forecasting rogue waves can be very complex, the goal of the global satellite measurement project is to improve forecasting by looking at the differences between wave models and actual observations, said Wolfgang Lengert, ERS mission manager for the European Space Agency,
During the last two decades, more than 200 supertankersships over 200 meters (656 feet) longhave sunk beneath the waves. Rogue waves are thought to be the cause for many of these disasters, perhaps by flooding the main hold of these giant container ships.
In a single week in winter 2001, two tourist ships were hit by rogue waves in the South Atlantic. The Bremen and the Caledonian Star had their bridge windows smashed by the errant wall of water reaching 30 meters (98 feet) high.
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