Tuesday, September 14, 2010
September 14, 2010 : Great Pacific Garbage Patch
Great Pacific Garbage Patch
The Great Pacific Garbage Patch, also described as the Pacific Trash Vortex, is a gyre of marine litter in the central North Pacific Ocean located roughly between 135° to 155°W and 35° to 42°N. The patch extends over a very wide area, with estimates ranging from an area the size of the state of Texas to one larger than the continental United States; however, the exact size is unknown. This can be attributed to the fact that there is no specific standard for determining the boundary between the “normal” and “elevated” levels of pollutants and what constitutes being part of the patch. The size is determined by a higher-than normal degree of concentration of pelagic debris in the water. Recent data collected from Pacific albatross populations suggest there may be two distinct zones of concentrated debris in the Pacific.
The Patch is characterized by exceptionally high concentrations of pelagic plastics, chemical sludge, and other debris that have been trapped by the currents of the North Pacific Gyre. Despite its size and density, the patch is not visible from satellite photography since it primarily consists of suspended particulates in the upper water column. Since plastics break down to ever smaller polymers, concentrations of submerged particles are not visible from space, nor do they appear as a continuous debris field. Instead, the patch is defined as an area in which the mass of plastic debris in the upper water column is significantly higher than average.
Like other areas of concentrated marine debris in the world's oceans, it is thought, the Great Pacific Garbage Patch formed gradually as a result of marine pollution gathered by oceanic currents. The garbage patch occupies a large and relatively stationary region of the North Pacific Ocean bound by the North Pacific Gyre (a remote area commonly referred to as the horse latitudes). The gyre's rotational pattern draws in waste material from across the North Pacific Ocean, including coastal waters off North America and Japan. As material is captured in the currents, wind-driven surface currents gradually move floating debris toward the center, trapping it in the region.
The size of the patch is unknown, as large items readily visible from a boat deck are uncommon. Most debris consists of small plastic particles suspended at or just below the surface, making it impossible to detect by aircraft or satellite. Instead, the size of the patch is determined by sampling. Estimates on size range from 700,000 square kilometres (270,000 sq mi) to more than 15,000,000 square kilometres (5,800,000 sq mi) (0.41% to 8.1% of the size of the Pacific Ocean), or, in some media reports, up to "twice the size of the continental United States." Such estimates, however, are conjectural based on the complexities of sampling and the need to assess findings against other areas.
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