The Atlantic Garbage Patch, Surveyed

August 20, 2010

Last August, I posted a couple of notes about Project Kaisei, an expedition to the Great Pacific Garbage Patch, a huge collection of plastic bottles and miscellaneous rubbish, concentrated by prevailing winds and currents into an area of the North Pacific ocean about the size of Texas.  Then in June, the existence of a similar Atlantic “garbage patch” was confirmed by a French ocean survey in the Sargasso Sea.

The “Wired Science” blog at Wired now has a report of a project that uses 22 years’ worth of survey data to map the extent of the Atlantic patch.

Scientists have gathered data from 22 years of surface net tows to map the North Atlantic garbage patch 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.

Most of the pieces of plastic found were small — less than half an inch long.  (The nets used would not capture pieces smaller than about 0.01 inch.)  The highest concentrations of plastic were found in the area between the latitude of Virginia and the latitude of Cuba.  Because of the routes taken ny the collecting ships, the east-west extent of the patch is less clearly known.  However, experiments with drift buoys tracked by satellite suggest that most of the plastic originates from the east coast of the US.

One possibly hopeful sign is that the average concentration of plastic has not increased over the 22-year survey period, although consumption of plastics certainly has.  Possibly, this reflects the plastic being gradually broken down into pieces too small to collect.

I hope that at some point we can convince people to stop using the oceans as a trash can.

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