Real-time Earth and Moon phase

Friday, May 08, 2009

Monster wave's secret?

Here's a new BBC video :



and the narration written by its Earth News Editor Matt Walker:
A huge ocean wave has been filmed from beneath the surface, revealing features never before captured on camera.

The remarkable video, which will be shown as part of the BBC Natural History Unit's new series South Pacific, was filmed in super slow motion using a high-definition camera.

It reveals the hidden power of a four-metre-tall monster barrel wave.

It also shows the first images of underwater spiralling vortices created by the wave's action.

The wave was filmed off the coast of Pohnpei in the Caroline Islands, part of the Federated State of Micronesia.

The location is well known in the international surf community. Some of the biggest waves in the world break on South Pacific islands.

The storm swells that create these waves travel more than 5,000km to break on their shorelines.

Super slow mo

"I really wanted to slow the wave down, so it was like being there, immersed in that environment," says the BBC's Huw Cordey, series producer of South Pacific.

"I wanted to capture the scale of the event."

Doing so took special skills and equipment. Australian cameraman Bali Strickland, renowned for filming expert surfers at some of the best surfing sites in the world, had to float in the water as the wave passed over him.

He filmed the wave using a £66,000 ($100,000) high-speed camera that captures the action at 20 times slower than normal speed, and in high definition.

The kit required a special housing unit designed and built by German specialist high-speed cameraman and technician Rudi Diesel.

Until this film, no one had ever tried using this type of camera underwater before.
The spectacular results show the wave barrel closing over Australian big wave surfer Dylan Longbottom, who rode the wave to illustrate the scale and power of the water.
Clearly visible are long underwater vortices created by the moving wave, a feature the BBC team believes has never before been caught on camera.

"So much is revealed by slow motion," says Mr Cordey.

"We saw these vortices on one shot, which I don't think anyone has noticed before. It opens up this huge insight into the birth of a wave."

The vortices only appeared once, despite the team filming more than 10 waves, he added.

"Maybe it's when the wave gets to a certain height or size. It wasn't a scientific experiment, so its difficult to judge. But its interesting we only saw it the one time."

Origins of surf

The location of the shoot is appropriate as the South Pacific is reputed to be the place surfing started some 1,500 years ago.

The giant waves have since inspired the culture of the human colonisers of the islands.

The waves start as a swell on the opposite side of the ocean, arriving days later. During the course of their journey, they move from travelling over deep water to water just two metres deep.

"That's what causes them to rear up and barrel," explains Mr Cordey.

The clip will be broadcast as part of the first programme of the six-part landmark series.

The South Pacific programmes explore the isolation of the region's islands, the extraordinary journeys wildlife and humans have taken to reach these remote specks of land and what happened to both after their arrival.

Upcoming programmes will include footage of undersea volcanoes attempting to form new islands, tiger sharks snatching newly fledged albatross chicks and bizarre human rituals that involve people jumping from 20-metre wooden scaffolds with only forest vines to break their fall.

It takes several views to get a feeling on what's going on. The title of the news was "Monster wave gives up its secrets." I still can not quite figured out those live vortices yet. The study of vortex is an exciting branch of Fluid Mechanics. As they say it wasn't a scientific experiment, but now the ball is in theoreticians' court to theorize those vivid wave generated vortices in three dimensions. (This Wikipedia article on Votex should be a good starting point for anyone interested in further exploration.)

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