Wednesday, February 21, 2007

Rogue Waves

Centuries ago, the "hole in the ocean" was the folklore of grizzled old sea dogs. Today, oceanographers know that the catastrophic phenomena -- which they call "freak" or "rogue" waves -- do indeed exist, and they even have a good idea of what causes the towering waves. While always unexpected, freak waves tend to occur more often in particular areas, such as off the eastern coast of South Africa (where the Waratah disappeared and the Oceanos sunk, as described in the SAVAGE SEAS episode "Killer Waves"), in the Gulf of Alaska, and off the Florida coast. That has given oceanographers vital clues about their origin.

The prevailing theory holds that freak waves can result when strong, high storm waves slam headlong into a powerful current traveling in the opposite direction. The interaction can push together the storm swells, so that their frequencies superimpose, creating one tremendously powerful wave that can reach a height of 100 feet or more. (The "hole in the ocean" describes the deep trough that precedes this steep crest of water.)

Off the coast of South Africa, north-tracking storm waves generated off of Antarctica (particularly when a low-pressure system is settled over the area) slam into the Agulhas current, which sweeps southward down the coast. The rogue waves that are generated severely damage two to three tankers every year. Off Florida, freak waves are born from the interaction of the northeast-flowing Florida current and North Atlantic storm waves butting up against the current.

To reduce the damage caused by rogue waves, oceanographers are trying to develop techniques to predict when and where they'll strike. Scientists at the University of Miami, for example, are using radar images snapped by NASA satellites to chart the formation and location of the deadly waves. Radar measures how light is scattered off the ocean surface, and can produce a picture detailing the height, length, and direction of travel of ocean surface waves -- including the occasional freak wave. The researchers hope eventually to be able to transmit that information in real time to cruise and cargo ships, steering them clear of danger.

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