Scientists say computers are helping them solve one of the mysteries of the swirling collection of plastic trash known as the Great Pacific Garbage Patch, namely where is it all coming from?
Since the massive floating patch of trash was discovered in 1997, researchers have been trying to identify what countries or regions might be most responsible for the plastic ocean pollution.
Now Australian researchers say math, and computer models, are giving them clues that can help them sort out of the Pacific patch between Hawaii and California, and the other four in the world's oceans that exist in the middle of circular marine currents known as gyres that collect and hold on to floating plastic debris.
Their surprising findings show that such plastic pollution can travel large distances and that that ocean garbage patches are not as isolated from each other as previously believed.
"In some cases, you can have a country far away from a garbage patch that's unexpectedly contributing directly to the patch," says University of New South Wales mathematician Gary Froyland.
For example, he points out, ocean debris from Mozambique and Madagascar -- countries whose coastlines are on the Indian Ocean -- can end up in the southern Atlantic.
The models can also help yield insights into the time it might take plastic trash originating in Australia to flow into northern Pacific waters, the researchers say.
Their research suggests the ocean garbage patches cannot by addressed individually but must be considered in terms of global ocean connections, they say.
What scientists have long thought of as boundaries between the world's great seas, generally delineated by fast-moving and fixed currents, are not what are traditionally depicted on maps, the researchers point out.
Portions of the Indian and Pacific oceans are in reality more closely linked to the southern Atlantic, but other parts of the Indian Ocean share a connection with the southern Pacific, they say.
"The breaking of the geographic ocean boundaries should shift the way people think of where oceans begin and end," Froyland says. "The interactions that we've shown between the different oceans shows that no ocean is isolated and that local effects can have impacts far from the source."
A re-drawing of ocean boundaries will help in future tracking and identification of the floating garbage patches, the researchers say.
"We first wanted to see where the boundaries are, the next step is to study the amount of plastic crossing these boundaries," oceanographer and research team member Erik van Sebille says.