The magic of science writing: ocean eddies become black holes

wikipedia: Maelstrom - Harry Clarke

My friend Steve sent me an article titled Black Holes aren't just in space - they have an equivalent here on Earth. While I don't really need to point out that MSN is not the most scientific of news sources, this article provides interesting insight into how journalism can really distort one's view of valid scientific work. Plus, the science behind the article is interesting. 

MSN's version of the story is short. It says

Imagine a black hole-like swirl of water in the ocean, 90 miles across and so powerful that nothing getting too close can escape the vortex. This is not the stuff of science fiction. Scientists have known for a long time about what they call massive "coherent eddies," but George Haller at ETH Zurich and Francisco Beron-Vera at the University of Miami have come up with a mathematical technique for defining the eddies' boundaries. Not only can they detect the location of the eddies, but they say that mathematically the long-term events are equivalent to black holes in outer space. They function as huge, drifting transport containers, capturing foreign objects like small organisms or trash or oil and moving them. The eddies also move water that is a different salt content or temperature than the surrounding water.

I actually think the MSN article does a good job and doesn't have too much misinformation. But after a title of Black Holes aren't just in space - they have an equivalent here on Earth, one really comes away with an impression of something far grander and far scarier than it really is. But don't get me wrong, the science here is actually quite fascinating. One of the most famous spots for these coherent 'black hole' ocean eddies is in the Agulhas Current around the tip of Africa. As this current of water from the Indian to the Atlantic Ocean meanders it sometimes loops back on itself and the enclosed water becomes a coherent vortex and spirals off into the Atlantic Ocean. Coherent means that water inside the vortex and the water outside do not mix. Because of this, the temperature, salinity, and even biology of these eddies can be very different from their surroundings. They collect phytoplankton, fish, and garbage, and become their own little ecosystem that can persist for about a year. If, however, one of the objects trapped inside happens to be you, you have a distinct advantage in that unlike phytoplankton, you (hopefully) can swim, or better yet, sail away in a boat, and you thus certainly have a chance of escaping. Though I will admit, being in such a vortex could certainly cause problems with navigation and yes, they often form around Bermuda (portals to another dimension not included). 

The original study by George Haller and Francisco Beron-Vera actually started the analogy to black holes. They apply math taken from general relativity (the science of gravity, black holes, spacetime, etc.) to define the boundary of the 'black hole' eddies as the boundary from which water does not escape, much like the boundary in a real black hole from which light cannot escape. But of course, in the media, 'mathematically equivalent to black holes' gradually transforms into 'like a black hole' which gradually transforms into 'black holes in the ocean!' Something to keep in mind next time you read about science, even if it doesn't sound as farfetched as this. 

Note on the picture: This is an illustration from Edgar Allan Poe's A Descent Into Maelström which the authors of the study offer as literary inspiration to go along with their work.