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North Pacific Gyre, a Vortex in the Sea
The North Pacific Subtropical Gyre is one of five oceanic gyres, massive vortexes in the open ocean that are caused by wind-driven surface currents. The North Pacific Gyre is formed by four ocean currents: the North Pacific Current, California Current, North Equatorial Current and Kuroshio or Japan Current. Flowing clockwise, these currents create an enormous circle in the sea between the west coast of the US and Japan. Varying in width and depth, the speed of these currents ranges from 1 to 4 km/hour.
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The Great Pacific Garbage Patch
Also known as the Pacific Trash Vortex, the Great Pacific Garbage Patch is an area of floating trash estimated to be in excess of 600,000 square miles, or twice the size of the state of Texas, and weighing 3.5 million tons.
Approximately 80% of the debris within the Garbage Patch comes from land, washing down from rivers and storm drains, or being swept off beaches by tides. The remaining 20% is from cargo containers that fall from oceangoing ships and spill their contents. Floating trash, the vast majority of which is plastic, is captured by rotating ocean currents and accumulates within the North Pacific Gyre.
There is a similar phenomenon, the Atlantic Garbage Patch, occurring in the Sargasso Sea between Bermuda and the Azores, in an area known as the North Atlantic Subtropical Gyre.
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Large quantities of trash wash up on islands within the North Pacific Gyre and shorelines surrounding it, such as those of Alaska and Japan. Piles of garbage up to 10 feet deep cover the beaches of some islands of the Hawaiian archipelago.
Marine debris poses a deadly threat to marine and coastal ecosystems. Hundreds of thousands of sea turtles, seabirds and marine mammals are killed annually when they ingest or become tangled in plastic debris. On the Midway island Wildlife Refuge, located on an isolated atoll in the middle of the Pacific, 40% of the 500,000 albatross chicks that are born each year die of starvation or dehydration, their stomachs filled with plastic debris that is mistaken for food. While it may break up into smaller pieces, the plastic does not biodegrade, and will remain in the ocean indefinitely.
In addition to the risks presented by ingestion and entanglement, the plastic also creates a toxicity hazard. Although the use of toxic chemicals such as polychlorinated biphenyls (PCBs) and the pesticide DDT has been banned or restricted, they do not degrade and still remain dispersed in seawater. These chemicals are hydrophobic, meaning they do not dissolve in water, but they are readily absorbed by oil-based plastic, concentrating them up to a million-fold. Tiny pieces of plastic containing the toxins are ingested by fish or other sea animals, which are in turn eaten by larger creatures. The concentration of toxins is amplified as it moves up the food chain, a process called biomagification.
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Prevention and Restoration Efforts
The problem of trash in the seas is not limited to the North Pacific; debris is found throughout the world's oceans. National and international conventions and agreements have been implemented to reduce the amount of plastic debris that ends up in the marine environment. The US National Oceanic and Atmospheric Administration (NOAA) is investigating potential cleanup strategies. Many organizations are dedicated to restoring the oceans, including the Environmental Cleanup Coalition, the Algalita Marine Research Foundation, and the Ocean Conservancy.
Expanded waste reduction, recycling and reuse programs are critical to lessen the amount of plastics that find their way into the sea. Individuals can play their part by spreading the word about the global problem of marine debris, reducing the amount of plastic they use, taking care to recycle or dispose of plastic trash properly, and pitching in to help with beach or river cleanup programs in their area.
Learn more about how scientists are studying this phenomenon in 'Voyage to the Great Pacific Garbage Patch'.
Silverman, Jacob. "Why is the world's biggest landfill in the Pacific Ocean?" HowStuffWorks.com September 19, 2007.
Hohn, Donovan. "Sea of Trash." New York Times Magazine, June 22, 2008.
Bird, Winifred. "Oceans Awash in Toxic Seas of Plastic." The Japan Times, March 22, 2009.