Giant Waves

Giant Waves

This article relates to The Wave

Giant waves were once the stuff of nautical tall tales, filed alongside stories of mermaids and giant squid, but today we know better.

The force of waves is hard to comprehend. According to The Wave, an 18 inch wave can topple a wall built to withstand 125-mph winds; a breaking 100-foot wave packs 100 tons of force per square meter. In short, those who encounter giant waves rarely live to tell the tale! According to the 1995 MaxWave Project, 200 super carriers have been lost in the last 20 years, many believed to be due to rogue waves.

The first measurable recordings of giant waves came from oil rigs, such as the Ocean Ranger, a 337 foot high oil rig located off Newfoundland which was struck by a wave in 1982 and capsized. There is no record of the size of the wave but the rig was built to withstand 110 foot seas. Then, in 1995, a rig in the North Sea was hit by a freak 85 foot wave, more than twice the height of the other waves in the storm. The rig survived but its engineers were sent back to the drawing board as their wildest calculations had never allowed for waves of that size. These events shifted the emphasis from explaining why giant waves could not exist to working out how they did.

At least a partial answer to the question of how was provided by the crew of the RSS Discovery, who barely lived to tell the tale. In January 2000, Discovery left port in Southampton, England, on what was intended to be a typical three week scientific trip to Iceland and back. Ten days later the 47 scientists and crew found themselves trapped in a series of huge storms 250 miles off the coast of Northern Ireland in an area east of Rockall. For more than five days Captain Keith Avery steered his ship directly into the waves, as to be hit broadside would be almost certainly fatal. Not only were these the worst waves he'd encountered in 30 years at sea, but they defied the normal course of nature by continuously rearing up from different directions.

Somehow, Captain Avery managed to turn the ship around and steer safely back to Southampton, but the trip was not a loss. Ringed with instruments, Discovery had recorded the wave action precisely: The significant wave height (the average of the largest one-third of the waves) was 61 feet, with many waves spiking far beyond that, up to 100 feet. This was far beyond anything the weather forecast had predicted; in short, waves of that size should not have existed in those conditions. That they did was now abundantly clear, but how?

The answer, provided by the data from Discovery, is that giant waves are, at least in part, the result of resonance. Resonance is aparently devilishly difficult to explain mathematically but is analagous to a child pumping his legs on a swing, boosting his height on each pass with erratic bursts of energy - in the ocean, wind energy works in the same way boosting the waves to ever greater heights.

But resonance would appear to be just part of the picture as it does not explain freak waves that are three to four times the size of their neighbors. Nor do scientists understand how global climate change is effecting these waves. Clearly there is much to learn about the 71% of the earth that is covered by salt water - and answers to some of our questions can be found inside the fascinating and abundantly readable The Wave!

Meanwhile, a growing body of surfers actively seek out giant waves; Laird Hamilton is perhaps the most famous, and is heavily featured in The Wave:

Filed under Nature and the Environment

This "beyond the book article" relates to The Wave. It originally ran in October 2010 and has been updated for the May 2011 paperback edition. Go to magazine.

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