(Photo: Mike Clarke/Getty Images)

How All That Plastic Got to the Ocean’s Great Garbage Patches

A new analysis shows how countries far from plastic pollution may be contributing to the problem.
Sep 8, 2014· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

It’s no secret that much of our plastic trash ends up in the five great garbage patches, swirling through the world’s oceans, choking and trapping birds, sea turtles, and other marine life. What has not been known is where that plastic bottle that fell out of your backpack at the beach ends up.

Until now.

Australian oceanographers have built an online tool that allows people to predict how plastic pollution travels in ocean currents. That means scientists are a step closer to pinpointing the amount of trash and who is responsible for that plastic pollution coming from a particular country.

“We can’t yet say this is Chinese plastic or American plastic,” said Erik van Sebille, an oceanographer at the University of New South Wales in Sydney. “To hold countries accountable, we need to know something about the currents, and we need to know where the plastic is at this moment, even outside of the garbage patches.”

A rubber ducky dropped into the Pacific Ocean off the California coast, for instance, could wash up on Japan’s shores 10 years later. Or it could resurface in a different ocean altogether.

Scientists discovered long ago that water circulates in the ocean by sinking in some places and rising in others, like a roller coaster.

Plastic in the ocean is buoyant, so it doesn’t move with that motion. “The plastic is essentially like the turd that won’t flush; it just sits there on the surface,” said van Sebille.

What was not known was the size of each catchment area—the toilet bowl where all that plastic garbage is taken by ocean currents.

Last year, van Sebille and his colleagues published a paper showing that the garbage patches are not black holes. Their borders are leaky, and garbage can flow from one catchment area to another over time.

The new paper, published in the journal Chaos, shows that parts of the Pacific and Indian Oceans are most closely coupled to the South Atlantic, while another sliver of the Indian Ocean really belongs in the South Pacific.

Van Sebille pointed out that though resources should be deployed to clean up the garbage patches, plastic trash does the most harm near the coasts home to sea turtles, manatees, dolphins, and birds.

“By the time it gets to a garbage patch, the damage is already done,” he said.