How So Much Plastic Got Into the Frozen Arctic Sea

Photograph by Peter Broecke/Getty Images

The Arctic Ocean is considered one of the world’s “last pristine ecosystems.” That’s why Rachel Obbard, a Dartmouth University professor who studies polar ice and materials science, was shocked to find that Arctic sea ice contains large quantities of plastic and synthetic particles. “I used to think of Arctic sea ice as unaffected by man-made pollutants,” she says. “It’s not the case.”

In a study published in the open-access journal Earth’s Future, Obbard and her colleagues write that more than a trillion bits of plastic may be released into the ocean over the next 10 years as global warming speeds the melting of Arctic ice. Obbard stumbled upon the microplastics while examining four enormous samples of so-called “sea ice,” which generally forms during the winter and largely melts away during the summer. Most sea ice has been frozen from two to five years and measures roughly one to five meters from surface to sea level. The samples, each about 1 meter thick (3.2 feet), had been collected from locations roughly 1,000 kilometers apart during Arctic expeditions in 2005 and 2010.

“I melted [the ice] through a very fine filter,” Obbard explains. “There was some sediment, like sand, and some microorganisms … and then these little brightly colored pieces of plastic.” Most of the particles were roughly the size of a pin head and made from commonly-used synthetic materials such as polyester, nylon, and polyethylene. The researchers found anywhere from 38 particles to 234 particles per cubic meter of ice.

Obbard and her colleagues believe that micro-plastics typically land in the ocean in one of three ways: “One way is through laundry,” she says: “The lint particles that come off in your washing machine and then get washed out with the water.” A second type of particles results from fragmentation in the ocean of larger plastic waste such as water bottles and fishing nets. The last major source is probably waste from companies that use small plastic particles to manufacture larger items.

It’s unclear whether the majority of the plastic flows into the Arctic from the Pacific Ocean or the Atlantic Ocean, says Obbard. The particles are found in higher concentration in ice than in water because they’re light and tend to float at the surface of the ocean, where they get trapped in ice as the water freezes.

The potential ecological hazards of the synthetic fragments to Arctic marine life are unknown, but Obbard’s discovery may help solve a longstanding mystery: Humans produce huge amounts of plastic but cannot account for where much of it ends up. “Polar sea ice represents a major historic global sink of man-made particulates,” the study suggests.

To make matters worse, plastic lasts forever. Even most biodegradable plastics don’t degrade in seawater because they require the relative warmth of soil or a compost heap. “We have managed to pollute the entire earth,” says Obbard. “There’s no place that’s exempt.”

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