Prof Rachel Obbard

The Arctic Ocean is considered one of the world’s “last pristine ecosystems.” That’s why Rachel Obbard, a Dartmouth [engineering] 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.