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An Odious Odyssey
A new scientific model tracks trash from sea to shining sea.

You’ve probably heard about the Great Pacific Garbage Patch—millions of pieces of plastic and other debris swirling around between Hawaii and California. The only thing more revolting than a massive swirl of marine garbage is the realization that there are actually five massive swirls of marine garbage. The South Pacific, Indian, and North and South Atlantic oceans all have their own prodigious aggregations of plastic.

You might picture these patches as floating islands of refuse, but they are more like a plastic soup of bits of broken-down grocery bags, dissolved water bottles, and the microbeads found in some face washes. The sea, it would seem, is the last stop in humanity’s collective waste stream.

We are all at fault here, but on a specific level, we have no idea where this stuff comes from. Every country on earth overuses plastic, and way too much of it winds up in waterways and the oceans. Once ocean currents sweep up plastic, tracking it becomes incredibly difficult (see “Needle in a Landfill”). But track it we must, if we’re going to figure out how to control this flow of garbage. Without knowing the source, it’s far too easy for individual countries to play noes goes with regulating marine trash.

Donovan Hohn dramatized the interconnectedness of the oceans in his remarkable 2011 book Moby Duck, which chronicles the voyages of about 28,000 rubber duckies that fell into the sea in 1992 when waves rocked a Chinese container ship on its way to Seattle. Hohn followed the trail all over the world in an epoch quest to track the bright yellow duckies, which had attracted the interest of scientists who study ocean currents.

Romantic as that sounds, there’s now an easier way. Mathematicians at Australia’s University of New South Wales described in a recent paper how they built flow models showing where sea garbage would go. For instance, bits of trash thrown from the shores of Mozambique would most likely end up in the South Atlantic garbage patch—not in the much closer Indian Ocean patch. The model will also help researchers determine how the garbage patches “share” with one another. (That’s right—the patches are so huge, and the ocean currents so complicated, that trash can skip and hop its way around the world from garbage patch to garbage patch.)

Here’s one fascinating nugget of detail hidden among the mathematic nerdiness harnessed to create the models: Do you remember when the IBM computer Deep Blue defeated chess grandmaster Garry Kasparov? There was a widespread misconception that, before making a move, the computer considered every possible option, playing out all the hypothetical games that would result from each choice.

In fact, Deep Blue was not fast enough to do that in the time allowed in a chess match. The genius of Deep Blue’s programming was that the computer knew which options to consider and which weren’t worth considering. One of the most important aspects of computer programming is limiting what the computer has to compute.

Well, that’s exactly what the mathematicians did to track ocean garbage. It is theoretically possible to build a simulation that could track every particle in the oceans’ waters—and the nearly infinite number of paths they could take. But that would tax even the most powerful supercomputer. Instead, the researchers simplified the model, breaking the oceans into seven regions. The waters of those regions mix only minimally, meaning that the computer can view the system as a few discrete chunks of water rather than countless particles.

One result of this modeling is that it shows our current maps are a poor estimation of how water actually moves in the ocean. Portions of both the Pacific and Indian oceans should actually be considered part of the southern Atlantic. Another bit of the Indian Ocean is more naturally part of the southern Pacific. Cartographers, take note!

There’s more to this study than helping you figure out where to drop off your message in a bottle. Understanding the dynamics of the world’s great garbage patches could help target cleanup efforts, shame the worst polluters, and stem the flow of our own contributions. Then maybe one day we all can proclaim: “The duck stops here.”

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Brian Palmer covers daily environmental news for OnEarth. His science writing has appeared in Slate, the Washington Post, the New York Times, and many other publications. MORE STORIES ➔