Garbage that reaches the ocean from the west coast of the United States and from the east coast of Japan is carried by currents—including the California Current, the North Equatorial Current, the North Pacific Current, and the Kuroshio—into the North Pacific subtropical gyre, the clockwise rotation of which draws in and traps solid matter such as plastics. Some 80 percent of the plastics in the garbage patch come from the land. It takes years for debris to travel from the coasts to the gyre, and, as it is carried along, photodegradation causes the plastics to break down into tiny, nearly invisible bits. While there are some larger objects that come from ships and offshore oil rigs, the garbage patch could more accurately be described as a soup of microplastics. The dimensions and depth of the patch are continuously changing.
Scientists had been aware of the growing problem of plastic debris in the world’s oceans since the late 1980s. However, the Great Pacific Garbage Patch came to public attention only after 1997, when yachtsman Charles Moore, returning home after participating in the biennial Transpacific Race, chose a route that took him through the North Pacific subtropical gyre. He found himself traversing a sea of plastics. When he returned to the area the following year, he discovered that the patch had grown in both extent and density. Moore began making speeches and writing articles—notably a 2003 essay in Natural History magazine—and he changed the mission of the Algalita research foundation, which he had founded in 1994 to improve water quality along California’s coast. The organization now focuses on studying and publicizing the problem of plastics in oceans, in particular in the Great Pacific Garbage Patch. A 2006 series of articles in the Los Angeles Times about the garbage patch won a Pulitzer Prize and raised general awareness of the problem.
In 2015 and 2016 the Dutch-based organization Ocean Cleanup found that the density of the debris in the garbage patch was much greater than expected and that the plastics absorbed pollutants, making them poisonous to marine life. The Great Pacific Garbage Patch is the best known of several such zones, others of which exist in the Atlantic and Indian oceans.