Chuck Bednar for redOrbit.com – Your Universe Online
Scientists from the University of New South Wales in Australia have developed a new model which divides the world’s oceans into seven primary regions that experience little intermingling of water, but their research has also revealed the existence of flotillas of garbage located in large, circular ocean currents known as gyres.
One of those trash flotillas, the Great Pacific Garbage Patch, is a region of environmental concern located between California and Hawaii, the researchers explained. In this region, pieces of plastic are scattered all over the ocean surface, outnumbering plankton in that area of the ocean and posing risks to fish, turtles and birds if consumed.
It is believed to be one of five such locations, and according to the UNSW team, the new model could help determine which nations are to blame for the creation of each garbage patch. Their discovery is part of a larger study, published Tuesday in the journal Chaos, which investigates how well the ocean’s surface waters mix.
“In some cases, you can have a country far away from a garbage patch that’s unexpectedly contributing directly to the patch,” UNSW mathematician Gary Froyland said in a statement. For instance, even though Madagascar and Mozambique border the Indian Ocean, debris from those countries would likely flow into the south Atlantic.
Erik van Sebille, an oceanographer who worked with Froyland on the study, added that the new model could also help experts determine how quickly refuse leaks from one patch into another. As he explained, scientists “can use the new model to explore, for example, how quickly trash from Australia ends up in the north Pacific.”
Winds, differences in water temperatures, global salinity gradients and forces caused by the rotation of the Earth all play a role in forming fast-moving ocean currents, the study authors explained. Currents stir ocean waters, but they also act as barriers limiting how much water in different ocean regions can mix. They compare it to the blast of air at the entrance of an air-conditioned building, which keeps the cold air inside and the warm air outside from mixing.
Along with UNSW colleague Robyn Stuart, Froyland and van Sebille divided the world’s waters into seven primary regions marked by extremely little mixing of waters. The team borrowed mathematical concepts from a field known as ergodic theory (which has also been used to partition interconnected systems such as computer chips and the Internet) to complete their work without needing to conduct complex simulations.
“Instead of using a supercomputer to move zillions of water particles around on the ocean surface, we have built a compact network model that captures the essentials of how the different parts of the ocean are connected,” Froyland explained. Based on their research, some portions of the Pacific and Indian oceans are actually more closely associated to the south Atlantic, while another section of the Indian Ocean is actually linked to the south Pacific.
“The take-home message from our work is that we have redefined the borders of the ocean basins according to how the water moves,” added van Sebille. He and his colleague believe that the geography of these new basins could help scientists learn more about ocean ecology, and make it easier to monitor aquatic debris. They added that they believe their technique could also be used to model smaller-scale bodies of water such as the Great Lakes, or to predict how an oil spill could spread through the Gulf of Mexico.
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