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The Great Pacific garbage patch, also described as the Pacific trash vortex, is a gyre of marine debris particles in the central North Pacific Ocean located roughly between 135°W to 155°W and 35°N and 42°N.〔See the relevant sections below for specific references concerning the discovery and history of the patch. A general overview is provided in Dautel, Susan L. "Transoceanic Trash: International and United States Strategies for the Great Pacific Garbage Patch," 3 Golden Gate U. Envtl. L.J. 181 (2009)〕 The patch extends over an indeterminate area, with estimates ranging very widely depending on the degree of plastic concentration used to define the affected area. The patch is characterized by exceptionally high relative concentrations of pelagic plastics, chemical sludge and other debris that have been trapped by the currents of the North Pacific Gyre.〔For this and what follows, see Moore (2004) and Moore (2009), which includes photographs taken from the patch,〕 Despite its large area, it is of very low density (4 particles per cubic meter), therefore not visible from satellite photography, nor even necessarily to casual boaters or divers in the area. It consists primarily of a small increase in suspended, often microscopic particles in the upper water column. ==Discovery== The Great Pacific garbage patch was predicted in a 1988 paper published by the National Oceanic and Atmospheric Administration (NOAA) of the United States. The prediction was based on results obtained by several Alaska-based researchers between 1985 and 1988 that measured neustonic plastic in the North Pacific Ocean. This research found high concentrations of marine debris accumulating in regions governed by ocean currents. Extrapolating from findings in the Sea of Japan, the researchers hypothesized that similar conditions would occur in other parts of the Pacific where prevailing currents were favorable to the creation of relatively stable waters. They specifically indicated the North Pacific Gyre.〔"After entering the ocean, however, neuston plastic is redistributed by currents and winds. For example, plastic entering the ocean in Japan is moved eastward by the Subarctic Current (in Subarctic Water) and the Kuroshio (in Transitional Water, Kawai 1972; Favorite et al. 1976; Nagata et al. 1986). In this way, the plastic is transported from high-density areas to low-density areas. In addition to this eastward movement, Ekman stress from winds tends to move surface waters from the subarctic and the subtropics toward the Transitional Water mass as a whole (see Roden 1970: fig. 5). Because of the convergent nature of this Ekman flow, densities tend to be high in Transitional Water. ''In addition, the generally convergent nature of water in the North Pacific Central Gyre (Masuzawa 1972) should result in high densities there also.''" Day, etc... 1988, p. 261 (Emphasis added)〕 Charles J. Moore, returning home through the North Pacific Gyre after competing in the Transpac sailing race in 1999, came upon an enormous stretch of floating debris. Moore alerted the oceanographer Curtis Ebbesmeyer, who subsequently dubbed the region the "Eastern Garbage Patch" (EGP). The area is frequently featured in media reports as an exceptional example of marine pollution. The patch is not easily visible, because it consists of very small pieces that are almost invisible to the naked eye.〔Cecil Adams (Why don't we ever see pictures of the floating island of garbage? ) Straight Dope / Chicago Reader〕 Most of its contents are suspended beneath the surface of the ocean,〔Steve Gorman (Scientists study huge plastic patch in Pacific ) Reuters〕 and the relatively low density of the plastic debris is, according to one scientific study, 5.1 kilograms per square kilometer of ocean area (5.1 mg/m2).〔 A similar patch of floating plastic debris is found in the Atlantic Ocean, called the North Atlantic garbage patch. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Great Pacific garbage patch」の詳細全文を読む スポンサード リンク
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