The Great Pacific Garbage Patch is an area of environmental concern between Hawaii and California where the ocean surface is marred by scattered pieces of plastic, which outweigh plankton in that part of the ocean and pose risks to fish, turtles and birds that eat the trash. Scientists believe the garbage patch is but one of at least five, each located in the center of large, circular ocean currents called gyres that suck in and trap floating debris. Researchers from the University of New South Wales (UNSW), in Sydney, Australia, have created a new model that could help determine who's to blame for each garbage patch -- a difficult task for a system as complex and massive as the ocean. The researchers describe the model in a paper published in the journal Chaos, from AIP Publishing.

"In some cases, you can have a country far away from a garbage patch that's unexpectedly contributing directly to the patch," said Gary Froyland, a mathematician at UNSW. For example, the ocean debris from Madagascar and Mozambique would most likely flow into the south Atlantic, even though the two countries' coastlines border the Indian Ocean.

The new model could also help determine how quickly garbage leaks from one patch into another, said Erik van Sebille, an oceanographer who collaborated with Froyland on the Chaos paper. "We can use the new model to explore, for example, how quickly trash from Australia ends up in the north Pacific."

At the heart of the researchers' work on the origins and fate of floating rubbish lies a bigger question -- how well do the ocean's surface waters mix?