For years there has been one writing credit missing from my resume. I like to tell people that I have written for all the magazines that have “Science” in the title: Science, American Scientist, New Scientist, Science News (assuming you count their Web publication Science News for Kids). But I had never written for Scientific American. I felt like the rock band Dr. Hook and the Medicine Show, who complained in a hilarious hit song from 1973, “And we keep gettin’ richer / But we can’t get our picture / On the cover of the Rolling Stone.”

Well, I may not be gettin’ richer, but I finally did get my picture in this month’s (July 2013) Scientific American, on page 88, toward the end of my article called “Walls of Water.”

When asked what the article is about, I have two ways of answering. If the person asking me looks as if they can survive a little bit of mathematical jargon, I tell them that it’s about Lagrangian coherent structures. These are invisible structures in any smoothly flowing fluid (e.g. the ocean or the atmosphere) that separate fluid that will go in one direction from fluid that will go in another. You can think of them as continental divides, only they are constantly on the move. They are remarkably persistent; in the ocean they can remain intact for weeks or even months at a time.

For people who are more jargon-phobic, I say that my article is about the mathematics of oil spills. If you dump a bunch of oil into the ocean, as BP did during the Gulf of Mexico oil spill in 2010, how can you tell where it’s going to go? The answer is to look for the Lagrangian coherent structures, or “transport barriers” to use a simpler term. Computers can do this now.

Unfortunately, I think that the opportunity was largely missed in 2010. As far as I know there were no real-time forecasts based on transport barriers. If there had been, perhaps we could have told the people in places like Fort Myers and Sarasota that there was virtually no chance of oil washing up on their beaches.  But one thing we can be sure of is that there will be another big oil spill someday — it’s just a question of when, not whether. Perhaps the technique of identifying transport barriers will be sufficiently accepted by then to be used in real time by the NOAA or other forecasters.

I have just one slight regret about the article, which is that it took so long to come out. I actually wrote it back in 2011 — the first draft was finished more than two years ago. At that time, the Gulf oil spill was still very fresh in people’s minds. For reasons beyond my control, the article was delayed a very long time, so it’s not as topical now as it would have been then.

Fortunately, science doesn’t have to be topical to be good. The technique of Lagrangian coherent structures will still be around the next time we need it. Meanwhile, the transport barrier concept has applications to many other kinds of fluid flow — for example, the flow of blood in your heart. This is an example that I didn’t write about in the first draft, because the work hadn’t been done yet! So I was able to use the two-year delay to update the article a little bit.

Hope you like the article! Comments are welcome!

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