On New Year’s Day, 1995, an instrument off the coast of Norway measured a rogue wave 84 feet high. Now, scientists are recreating these waves – albeit in miniature – in the lab.
Rogue waves like these aren’t tsunamis. Instead, they’re unexpectedly large waves that appear among a population of smaller waves. As researchers continue to measure these mysterious events, they hope to get to the bottom of how rogue waves form.
The 1995 wave, also called the Draupner wave, was the first confirmed “rogue wave” or “freak wave” measured by scientific equipment. The 84-foot wave was over twice the size of the average tallest waves in the area where it was recorded. Since then, scientists have observed more freak waves, and have learned that they’re rather common. But even today, it’s unclear how these enormous waves form without some specific environmental force, like an earthquake, to drive them.
The researchers were able to create a wave with equal steepness to the Draupner wave, occurring in a similar out-of-the-blue scenario, using a round tank whose 168 wave makers can send waves in any direction. Typically, waves are limited to some height, after which they break, and the tip collapses over the rest of the waves. But the researchers noticed sets of waves crossing at 60 to 120 degree angles could cancel out the horizontal movement of the water – the “breaking” behaviour of a wave instead sent water upward like a jet.
Everyone else says this looks like the famous Hokusai “Great Wave” painting, presumably because a press release said so. I mean, they’re both waves, I guess. But the painting represents a real ocean wave, and the photo captures a small wave created in a tank in a lab – and that important distinction is the main limitation of the study. Ocean waves like the Draupner wave or the Hokusai wave occurred out in the real world, influenced by countless variables, and are hard to simplify into easy mathematical equations or lab experiments. The formation mechanism behind “freak waves” is likely more complex than a lab experiment alone will reveal. And indeed, the researchers point out in their paper that the Draupner measurements should be taken with a grain of sea salt, since they come with a level of experimental uncertainty.
But this experiment adds another factor to take into account when discussing these strange waves, the researchers write in the paper, published in the Journal of Fluid Mechanics. They argue that their results did a better job recreating the properties of the Draupner wave than past examples, such as this one from 2009.
Nature’s freaky, but damn, isn’t it interesting?
McAllister et al (JFM)