You've probably heard of the Great Pacific Garbage Patch, a circulating gyre of stewing plastic waste in the Pacific Ocean. You might even be familiar with the existence of other smaller, though equally concerning, garbage patches in the North and South Atlantic oceans.
But what about the Indian Ocean? Where does all of its plastic trash accumulate?
Alarmingly, scientists don't really have an answer to this question, despite the fact that more plastic waste is estimated to get dumped in the Indian Ocean than anywhere else on Earth.
Part of the reason for the mystery is that the Indian Ocean doesn't have as much monitoring technology in place to keep track of the problem as other oceans do. Another part of it, though, involves an environmental enigma. The Indian Ocean just doesn't seem to contain as much plastic waste as it should. So where does all of its plastic go?
To solve the puzzle, researchers recently embarked on the most comprehensive survey of Indian Ocean currents yet performed, by gathering information from more than 22,000 satellite tracked surface drifting buoys that had been released around all the world's oceans since 1979. Based on the drift patterns of these buoys, they were able to simulate pathways of plastic waste globally with an emphasis on the Indian Ocean, reports Phys.org.
Researchers found a few places where some of the plastic is probably amassing, such as in the Bay of Bengal, which is surrounded by population-heavy India in the west, Bangladesh to the north, and Myanmar and Thailand to the east. But overall, gyres don't seem to form in the Indian Ocean in the same way they do in other oceans.
"Our study shows that the atmospheric and oceanic attributes of the Indian Ocean are different to other ocean basins and that there may not be a concentrated garbage patch," explained lead author, Mirjam van der Mheen. "Therefore the mystery of the missing plastic is even greater in the Indian Ocean."
The models did reveal one major hint about the disappearing plastic, though. It turns out, the Indian Ocean has a leak, and a lot of its plastic might be seeping out into another ocean, the South Atlantic.
"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," said van der Mheen. "These strong winds push floating plastic material further to the west in the southern Indian Ocean than they do in the other oceans."
In other words, a lot of the plastic from the Indian Ocean is probably sliding past South Africa and getting added to the soup in the South Atlantic garbage patch.
The findings highlight the need for global tracking systems of plastic waste, as the world's garbage patches are not insulated whirlpools of trash. Rather, there exists a complex web of interconnected ocean pathways that can't fully be understood in isolation.
"As technology to remotely track plastics doesn't yet exist, we need to use indirect ways to determine the fate of plastic in the Indian Ocean," said Professor Chari Pattiaratchi, from University of Western Australia's Oceans Graduate School and the Oceans Institute.