Plastic garbage gyre


Islands of waste and carpets of garbage – a myth
The extensive and high concentration of plastic debris in the North Pacific has become known as the «Great Pacific Garbage Patch» or The Seventh Continent. But in fact it is made up neither of islands of waste nor of carpets of garbage that are visible on satellite pictures, but consists of cloud-like constellations of flotsam that tend to drift beneath the surface of the water. The floating material follows complex current gyres and, depending on the weather conditions, can be driven down from the surface to a depth of up to 30 meters. In stormy conditions hardly any plastic objects are to be seen on the surface. From a ship only the larger pieces are visible with the naked eye – and only if the ship is traveling slowly. This is one of the reasons why the phenomenon of the concentration of plastic in the sea remained undiscovered for so long.


Hawaii: more plastic than natural sand

The catchment area of the «Great Pacific Garbage Patch» extends along the entire North Pacific coast of China, Korea and Japan, to Russia and Alaska and as far as Canada and California. The surface sea currents carry the objects floating in the water into the still area of the gyre, where the flotsam can drift around for decades and where friction and the effect of sunlight cause it to break down gradually into smaller and smaller pieces.
The islands of Hawaii are positioned in the middle of the North Pacific. Depending on the time of year, the centers of the great North Pacific gyre shift north or south according to the prevailing wind. At times the currents wash enormous amounts of plastic flotsam onto exposed beaches on Hawaii. At present there is more plastic than natural sand on certain beaches, for instance on Kamilo Beach now known as «Plastic Beach» on the southwestern tip of Big Island. 

Kanapou Bay, Hawaii, US
Papahanaumokuakea Marine National Monument, Hawaii


Following the movements of plastic waste

The extensive three-dimensional systems of currents in the seas are produced by the rotation of the earth, wind movements, differences in pressure, temperature and salinity, as well as by the topography of the sea floor. Their complexity makes researching their path a demanding undertaking. In recent years various research centers have been developing methods and instruments to predict the strengths and paths of currents. The Global Drift Program from NOAA (National Oceanic and Atmospheric Administration, US) launched in 2005, represents the first project aimed at systematically compiling worldwide data on the various decisive parameters of current paths and climate. Special floating buoys, monitored by satellites, transmit data about their geographic position, salt content, air pressure, water temperature etc. to be evaluated in the research centers. This enables models to be developed that can, for instance, simulate the route taken by tsunami flotsam from Japan, or, for research expeditions, can determine the areas where the highest concentrations of plastic flotsam are likely to be found.

Predicted movement of the Japan Tsunami marine debris, SCUD-Modell (Surface Currents from Diagnostic) by Nicolai Maximenko and Jan Hafner.

 

Links:
NOAA Global Drifter Program, US
SCRIPPS Institution of Oceanography, San Diego, US / CA
International Pacific Research Center, Honolulu, US / HI

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