News on Rip Currents

“Calm in a Current”

Matthew Maury gathered an amazing amount of knowledge about ocean currents as long ago as the early 1800s. Maury’s study of the ocean’s major currents mattered a great deal to sailors on the high seas. One particular type of current matters a whole lot more to people like you and me, especially when we visit the beach. We’re talking about rip currents.

Rip currents occur when waves keep pushing more and more water up against shore. Eventually that water rushes back out to sea. And it does so with a lot of speed and force. Rip currents can pull a person out to sea at four meters per second. It is useless to try to swim against a rip current. Even Olympic gold-medalist Michael Phelps can swim only two meters per second, and that is in a calm pool. Surprisingly, it has only been in the last 40 years that scientists have begun to understand the basics of how rip currents and the surf zone work. And even then rip currents were thought to rush straight out to sea, like a river of water with straight sides.

Now, researchers are coming to some different conclusions. Or at least they are starting to wonder about what they thought they knew. In recent years, studies have shown that rip currents double back toward shore. From above they would look like a bloom instead of like a long narrow path. California oceanographer Jamie MacMahn dropped floating GPS devices into a surf zone. He discovered that the locators did rush out with a rip current, but then they circled back. In fact, the floaters had an 80-90 percent chance of being swept back in to shore.

Why does that matter? Because it might change official advice to swimmers. We’ve all been taught that it is best to swim across the current (parallel to shore) to escape a rip current. But experts now think that perhaps swimmers should be advised to simply tread water. They could be returned to shore more quickly and safely by simply letting the rip current do the work. “I’ve jumped in a lot of rip currents all over the world and always end up back onshore,” Mr. MacMahn told The New Zealand Herald. “If you swim parallel to shore—the traditional recommendation—you have a 50-50 chance of swimming into a strong current and becoming exhausted. But if you don’t fight it and just tread water, you have an 80 to 90 percent  chance of the rip current conveyor belt returning you to shore in three to six minutes. Many experienced surfers know this, and even talk about ‘riding the rip’.”

Lifeguards and safety experts will undoubtedly stay informed about new knowledge of the surf zone. And they will adjust their official advice accordingly.

by Rich Bishop [God’s World News]