According to scientists, a four-story-tall rogue wave that briefly appeared in the Pacific Ocean off the coast of Canada in 2020 was the "most extreme" example of the bizarre phenomena ever documented.

 Rogue waves, often known as freak or killer waves, are large waves that arise out of nowhere in the open ocean.

The rogue wave was discovered on November 17, 2020, around 4.3 miles (7 kilometers) off the coast of Ucluelet on Vancouver Island in British Columbia, by an oceanographic buoy owned by the Canadian-based research organization MarineLabs. According to a recent study published online on Feb. 2 in the journal Scientific Reports, the Ucluelet wave was around 58 feet (17.6 meters) tall, making it approximately three times higher than nearby waves. Rogue waves this enormous in comparison to neighboring swells are a "once in a millennium" occurrence, according to the researchers.

A rogue wave is at least twice as tall as the surrounding sea state — the average height of the waves in a given location at a given time. According to NOAA, researchers believe that rogue waves arise when smaller waves merge into larger ones, either as a result of high surface winds or changes in ocean currents generated by storms. According to the statement, the specific mechanisms underlying the bizarre crests are still a mystery.

The Ucluelet wave originated in a sea state of around 19.5 feet (6 meters), making it slightly less than three times the size of surrounding swells, the most dramatic size difference ever documented. "Only a few rogue waves in high sea states have been directly witnessed, and nothing on this scale. Such an occurrence is unlikely to occur more than once every 1,300 years "said Gemmrich.

The Draupner wave was the first official rogue wave discovered in Norway in 1995. Scientists had previously assumed the existence of rogue waves, and legends of sailors being caught out or even murdered by unusually enormous waves had long filled nautical folklore, but scientists had never observed them until that 1995 paper. Scientists have only investigated a few rogue waves since then, but they estimate that one forms every two days somewhere in the world's waters, researchers stated in the report.

The Ucluelet wave is not the biggest rogue wave ever discovered. The Draupner wave, for example, recorded a far larger 84 feet (25.6 m) in height. The sea state during the Draupner wave, on the other hand, was roughly 39 feet (12 m), making the rogue wave a little over twice as tall (rather than three times) as surrounding crests.

Rogue waves, such as the Ucuelet wave, are typically ignored. However, if a ship or oil rig is caught in one of these massive crests, the consequences might be deadly. "The unpredictable nature of rogue waves, as well as the shear intensity of these 'walls of water,' may make them extremely harmful to marine operations and the general public," said Scott Beatty, CEO of MarineLabs, in a statement.

According to a previous study, climate change may increase the severity and frequency of rogue waves. According to a study published in the journal Science Advances in June 2020, extreme wave conditions have already increased by 5% to 15% as a result of stronger winds and currents driven by rising ocean temperatures.