Perilous Times
Scientists map out huge floating 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.
Published: 7:00AM BST 20 Aug 2010
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.