Sailors often whisper of monstrous waves capable of sinking the most seaworthy ships, but oceanographers have written off such reports as exaggerations. Now a satellite study has turned up evidence that freakishly large waves are more common than scientists thought.
Within the past 2 decades, at least 200 cargo ships--200 meters or more in length--have been lost at sea. Eyewitnesses and survivors describe huge breaking walls of water, more than 25 meters high, sometimes rising up out of calm seas. Such freak waves and the conditions that cause them are poorly understood. Mathematical models suggest that the waves should occur only once every 10,000 years on average, but recordings from buoys and offshore oil platforms suggest they're much more common.
To investigate further, researchers from six European countries teamed up to conduct the first global census of freak waves. In a 3-week period, they used two satellites operated by the European Space Agency (ESA) to collect about 30,000 radar images, each capturing a 10-by-5-kilometer patch of ocean in 10-meter resolution. Last week, ESA released the team's preliminary findings: During the survey period, 10 massive waves--some nearly 30 meters high--were detected around the globe.The data are a good first attempt at estimating the frequency of freak waves, but more work needs to be done to confirm that the radar technique is reliable, says mathematician Harald Krogstad of the Norwegian University of Science and Technology in Trondheim. According to marine physicist Mark Donelan, director of the Center for Air-Sea Interaction at the University of Miami, the work could help researchers improve on the conventional statistical methods used to study waves. Those techniques are "not well adapted to identifying freak waves," he adds.In the next phase of the research, a project called WaveAtlas will use 2 years' worth of images to create a worldwide atlas of freak wave events. The ultimate goal is to find out how they are generated and which sea regions are most at risk.