Rogue wave , sometimes called a freak wave, is a rare ocean wave that forms unexpectedly and reaches an unusually large size. Scientists typically define a rogue wave as a wave that is at least twice as tall as the surrounding waves. In extreme cases, rogue waves can be several times as tall the surrounding waves. The chance of encountering a rogue wave is remote. But when such encounters do occur, they can threaten ships, offshore platforms, and other seaborne structures and activities.
Scientists know little about how often rogue waves occur. One study conducted by satellite counted only 10 rogue waves in the entire ocean over a three-week period. However, some scientists think the waves occur more often than this study indicated. Even so, rogue waves are still considered rare. Because of the small number of rogue waves, many oceanographers once dismissed reports of their appearance as sailors’ tales. Only since the 1990’s have scientists gathered concrete evidence that rogue waves exist.
Researchers do not know exactly how rogue waves form, but most think the waves have more than one cause. The simplest cause of a rogue wave may involve interference. Interference occurs when multiple waves move through the same area. The waves may push one another higher or cancel one another out. In this case, a rogue wave may simply occur in rare instances when normal interference causes a wave to pile up to extreme heights. Another possible cause involves a series of waves entering an ocean current moving in the opposite direction. The current may force the waves back on top of one another, forming one large wave. However, not all rogue waves can form in this manner. Some occur in the open ocean where there is no current at the surface. Some scientists think these waves, as well as some others, form by a more complicated mechanism.
The Italian navigator Christopher Columbus reported encountering a rogue wave as high as his ship’s mast on Aug. 4, 1498, near Trinidad. Scholars have investigated rogue wave encounters as a possible cause for a number of modern shipwrecks that left no surviving witnesses.
