Scientists map North Atlantic garbage patch

A huge garbage patch of floating plastic in the North Atlantic Ocean has been documented by scientists for the first time.

Plastic accumulated in regions called gyres, where currents circle and push water toward the centre, trapping the floating bits. There are five major gyres in the world, one in each major ocean

Scientists have gathered data from 22 years of surface net tows to map the North Atlantic garbage patch, which lies to the east of Bermuda, and its change over time, creating the most accurate picture yet of any pelagic plastic patch on earth.

The data were gathered by thousands of undergraduates aboard the Sea Education Association (SEA) sailing semester, who hand-picked, counted and measured more than 64,000 pieces of plastic from 6,000 net tows between 1986 to 2008.

"The highest concentrations that we observe in the North Atlantic garbage patch are comparable to that of the North Pacific, but we don't have enough data about the size of the North Pacific one to say whether they are comparable in size," said oceanographer Kara Law of SEA, lead author of the study published August 19 in Science.

"As far as I'm aware this is the most complete and long term data set for little bits of trash floating in the ocean," said oceanographer Miriam Goldstein of Scripps Institution of Oceanography.

The highest concentrations of plastic were found roughly from the latitude of Virginia to the latitude of Cuba. They estimate the average concentration of plastic in this area is about 4,000 pieces per square mile, though it is as high as 250,000 pieces per square mile in some places.

To determine where the plastic is coming from, researchers used data from more than 1,600 satellite-tracked drifting buoys deployed between 1989 and 2009 to map surface currents in the region. More than 100 buoys passed through the Atlantic plastic region, most originating from the eastern seaboard. In most cases, the buoys reached the plastic patch in less than 60 days.

Plastic accumulated in regions called gyres, where currents circle and push water toward the centre, trapping the floating bits. There are five major gyres in the world, one in each major ocean.

One surprising conclusion of the study found the concentration of plastic in the North Atlantic has remained fairly steady during the past 22 years despite a five-fold increase in global plastic production and a four-fold increase in the amount of plastic the United States discards.

No one knows how long plastic stays in the ocean or where most of it ultimately will end up. Sea animals such as birds and turtles often consume plastic, sometimes carrying it to land. Some likely will sink over time or wash up on shore.