A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Peter Fogg
Date: 2010 Oct 6, 18:06 +1100
October 6, 2010 - 3:21PM
Big waves .. make a big story.
So you are the captain of a boat and you are faced with a 530-metre wall of water, the size of the World Trade Centre, and you only have seconds to act - what do you do?
Well, according to a new book, The Wave: In Pursuit of the Rogues, Freaks, and Giants of the Ocean, it is best to charge straight at it, hoping you make it over.
Or if you are one of a few crazy surfers who travel the world seeking the ultimate wave, you could always strap in and hope for the best.
The new book uncovers the phenomenon of "rogue waves", which can peak at well over 30 metres, and are said to sink large ships, smash oil rigs and, like shown in a recent video, cause havoc to luxury cruisers.
Then there are the rogue waves of legend, such as one in Alaska in 1958, which some believe reached 530 metres.
The book's author Susan Casey writes that giant rogue waves have been, until recently, debated because scientists did not believe they existed.
And much of that disbelief came because there were very few people who had seen one.
As Ms Casey told online magazine Salon "people who encountered 100-foot [30.5-metre] rogue waves generally weren't coming back to tell people about it" while anyone who spoke of survival "were thought to be exaggerating".
But improvements in technology, better weather radars and accurate laser measuring devices have allowed scientists to understand freak waves and measure them properly.
"In 1995, there was a well-recorded incident on this oil platform in the North Sea. On a day when there were 38-foot seas, an 85-foot wave popped up and battered the platform. It was measured by laser. That's when the scientists really turned to one another and said: 'What's going on out here?' she told Salon.
"By the laws of basic ocean physics and oceanography, that shouldn't happen."
Australian wave expert Tom Shand, who works at the University of NSW Water Research Laboratory, said rogue waves were almost impossible to predict.
Dr Shand said that rogue waves occurred "because you basically get a group of very steep waves travelling together ... and as they move along as a group they pass energy into a wave in the middle of the group and that leads to a very high and steep wave".
"A rogue wave is dangerous in the fact that it is so much bigger than other surrounding waves and not predicted by normal forecasts and so [it] can catch people and boats off-guard," he said.
"It's worth drawing the distinction between extreme waves and rogue waves. Rogue waves, as described above are waves more than twice as big as 'expected'.
"Extreme waves are consistently large waves caused by very large, rare events such as the recent storm south of Tasmania. Really large waves will occur when a rogue wave occurs during an extreme event ... The probability of this occurring at the same location as an observer - a boat, oil rig or wave buoy is low, but possible."
Dr Shand said the largest wave "officially" recorded was in 1933.
"I think the largest 'official' wave remains measured by the USS Ramapo in 1933 in the North Pacific - 112 feet measured by triangulation from the ship's bridge. They measured a 25.6-metre wave on the Draupner oil platform off Norway in 1995 and a 27.7-metre wave in the Gulf of Mexico during Hurricane Ivan in 2004," he said.
"There are many reported incidents where ships are damaged or capsized but quantifying the exact wave height is difficult."
But in her book, Ms Casey details epic tales of waves that have gone down in legend, which she claims includes the 530-metre monster in 1958, the size of the World Trade Centre.
"That was the largest wave ever recorded. It took place in Lituya Bay, a finger bay in Alaska," she told Salon.
"In this case, there was a big eruption on the nearby Fairweather Fault, which thrust parts of Alaska 47 feet in the air. Tonnes and tonnes of rock and ice went plunging down steep hillsides into this bay - it was like dropping a paving stone from a ladder in a bathtub.
"So here comes this 1740-foot splash wave. Scientists were able to determine exactly how big the wave was, because the forest and mountainsides were absolutely shaved.
"Three boats were anchored there at the time. Two of the boats had the presence of mind to go straight at it, which is really counter-intuitive but is the only way you survive. You have to get over the back of the wave before it crests. If you get caught in the lip, you're just going to be dead. That's what happened to the third boat."
Ms Casey said cruise ship operators were also becoming worried about waves getting bigger.
"Lloyd's of London is actually quite concerned about cruise ships. One of the guys said to me: 'This is a high concentration of risk. You've got 5000 people on boats that are getting bigger and bigger and they're going into gnarlier and gnarlier places.'
"They're all over Antarctica now, for example. Recently, one of the hardier cruise ships got hit by a 100-foot rogue wave and all of its navigation equipment got knocked out and windows got broken.
"During another recent cruise in Antarctica, all the people ended up in the water, which isn't a good situation. By the grace of god, there was another boat nearby."
Ms Casey also spent time with legendary big wave surfer Laird Hamilton, which included getting up close to 30-metre waves.
She believes that rogue waves will become more common as sea levels rise and temperatures increase.
"It's one of our most powerful forces of nature and it's basically unknown to us. That's a pretty precarious situation, especially if you consider that 60 per cent of the global population lives within 30 miles [48 kilometres] of the coastline," she told Salon.
"When the tsunami hit in 2004, people were asking, 'What's a tsunami? What do you mean a wave came ashore?'
"People acted like it had never happened before, but they actually happen pretty regularly."
Dr Shand said researchers were now looking at whether waves were getting bigger around Australian coast lines.
"While buoy records aren't showing a significant change one way or the other, a number of studies are suggesting more large Southern Ocean events like the one we had recently," he said.