Arctic sea ice has sopped up and stored large quantities of microplastic pollution from populated areas in the south, a new study has found.

Microplastics are tiny pieces of plastic from microscopic to fingernail-sized that have been found polluting oceans and lakes around the world over the past decade, but not so far north as the Arctic Ocean. Scientists are concerned about them because they tend to suck up and concentrate other pollutants in the environment, which enter the food chain when animals swallow microplastics.

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While much of the sea ice in the past has stayed frozen for many years, locking up pollutants and sediments trapped in them, more and more of that 'multi-year' ice is melting as the Arctic warms as a result of climate change. (Canadian Press)

Rachel Obbard, a materials scientist at Dartmouth College in New Hamphire, discovered that Arctic sea ice was contaminated with microplastics by accident when she melted the ice in order to count diatoms – microscopic algae that live under the ice.

"I was really shocked and saddened," she told CBC's Quirks & Quarks in an interview that airs Saturday. "I guess I, like most people, still consider the Arctic to be a pristine and remote area and clearly, our pollution has reached even it."

When the melted ice was filtered, the filter paper trapped not just sand and diatoms, but also a variety of brightly coloured particles.

"I saw a lot of small threads, some solid chunks in oranges and reds, and a bunch of small blue nodules," Obbard recalled.

Microplastics were found in all ice cores taken from four different locations in the Arctic that were far apart, suggesting that the microplastic contamination is widespread.

Hundreds of pieces per cubic metre of ice

Obbard estimated that there were between 38 and several hundred pieces of microplastic per cubic metre of sea ice.

A chemical analysis found the particles included a variety of different plastics, including polyethylene, polycarbonate and rayon.

The findings were published in the peer-reviewed open access scientific journal Earth's Future.

Obbard suspects they were carried into the Arctic by currents from populated areas in the south. She added that particles, including microplastics, tend to be concentrated by ice as it freezes.

While much of the sea ice in the past has stayed frozen for many years, locking up pollutants and sediments trapped in them, more and more of that "multi-year" ice is melting as the Arctic warms as a result of climate change.

"This suggests that there will be microplastic particles dumped back into the Arctic Ocean that have been entrapped in ice for several years," Obbard said.

She is now surveying the Arctic ice to find out how widespread the microplastic pollution is and what types of ice tend to concentrate it. She hopes to be able to identify the source of some of the microplastics, and also to find out how they are affecting Arctic organisms.