Despite the Indian Ocean being the single largest dumping ground for plastic waste, little is known about where it travels to after entering the ocean’s currents.
A new research initiative by the University of Western Australia aims to finally answer the question of where dumped plastics in the area end up by gathering more than 22,000 satellite tracked surface drifting buoys that have been released since 1979.
UWA’s Professor Chari Pattiaratchi said the every year, up to 15 million tonnes of plastic waste was estimated to make its way into the ocean through coastlines and rivers.
“This amount is expected to double by 2025,” he said. “Some of this waste sinks in the ocean, some is washed up on beaches and some floats on the ocean surface, transported by the ocean currents. As plastic materials are extremely durable, floating plastic waste can travel great distances in the ocean.”
Professor Pattiaratchi said some floating plastics were known to collect in the centre of subtropical gyres (large systems of circulating ocean currents) in ‘garbage patches’.
“Here, the ocean currents converge at the centre of the gyre and sink,” he said. “However, the floating plastic material remains at the ocean surface, allowing it to concentrate in these regions.”
Lead author, Mirjam van der Mheen who is undertaking the research as part of her UWA PhD said the research team found that unique characteristics of the southern Indian Ocean transport floating plastics towards the western side of the ocean, where it leaks past South Africa into the South Atlantic Ocean.
“Because of the Asian monsoon system, the southeast trade winds in the southern Indian Ocean are stronger than the trade winds in the Pacific and Atlantic Oceans,” she said.
“These strong winds push floating plastic material further to the west in the southern Indian Ocean than they do in the other oceans.