North Pacific Gyre

From Open Encyclopedia

The North Pacific Gyre (also known as the North Pacific Subtropical Gyre) is a swirling vortex of ocean currents comprising most of the northern Pacific Ocean.

The North Pacific Gyre is located between the equator and 50º N latitude. It is formed by the clockwise circular pattern of the prevailing ocean currents: the North Pacific Current to the north, the California Current to the east, the North Equatorial Current to the south, and the Kuroshio Current to the west. It occupies an area of approximately ten million square miles.

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Garbage

The centre of the North Pacific Gyre is relatively stationary (the area it occupies is often referred to as the horse latitudes) and the circular rotation around it draws waste material in. This has led to the accumulation of flotsam and other debris in huge floating 'clouds' of waste. While historically this debris has biodegraded, the gyre is now accumulating vast quantities of plastic. Rather than biodegrading, plastic photodegrades, disintegrating in the ocean into smaller and smaller pieces of plastic, and these pieces are trapped by the gyre and remain suspended in its centre. The photodegraded plastic can attract pollutants such as PCBs, and the floating particles also resemble zooplankton, which can lead to them being consumed by jellyfish and thus entering the ocean food chain. In parts of the gyre the ratio of plastics to zooplankton currently exceeds 6:1, that is, there are six times as many plastic particles as there are zooplankton.

Occasionally, shifts in the ocean currents release flotsam lost from cargo ships into the currents around the North Pacific Gyre, and this has led to predictable patterns of garbage washing up on the shores around the outskirts of the gyre. The most famous was the loss of approximately 80,000 Nike sneakers and boots from the ship Hansa Carrier in 1990: the currents of the gyre distributed the shoes around the shores of British Columbia, Washington, Oregon, and Hawaii over the following three years. Similar cargo spills have involved tens of thousands of bathtub toys in 1992, and hockey equipment in 1994.

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