Garbage patches in the ocean are sobering reminders of humanity\u2019s collective plastic pollution problem. Measuring up to thousands of kilometers across, the patches have been confirmed to exist in the Pacific and Atlantic Oceans, but not in the Indian\u2014a surprise, given that more plastic waste enters the Indian Ocean than anywhere else on Earth.<\/p>\n
According to a new study<\/a> led by Mirjam van der Mheen, a doctoral candidate at the University of Western Australia, the Indian Ocean\u2019s unique geography, ocean currents, and atmospheric conditions actually appear to be preventing waste from piling up in a garbage patch.<\/p>\n Pinpointing where all the plastic goes, says van der Mheen, is a huge challenge.<\/p>\n \u201cThe technology to remotely track plastics in the ocean does not yet exist,\u201d explains van der Mheen. \u201cThere aren\u2019t many measurements of marine plastic debris, so it is not straightforward to predict how plastic waste is transported once it enters the ocean.\u201d<\/p>\n Since they couldn\u2019t track individual pieces of plastic, the team used the next best thing: GPS data from more than 22,000 buoys that have drifted around the oceans since 1979. Running the data through computer simulations provided a picture of how floating objects are pushed around by currents and wind.<\/p>\n The simulations show that multiple physical forces prevent the formation of an Indian Ocean garbage patch. In the south Indian Ocean, an unusually persistent equatorial countercurrent flows from west to east across the basin, scattering a trail of submerged plastics all the way to Australia.<\/p>\n Additionally, strong easterly monsoon winds move buoyant surface debris in the opposite direction, toward the African coastline.<\/p>\n Because the south Indian Ocean\u2019s gyre extends just past the southern tip of Africa, plastics accumulate here briefly, then move out past South Africa into the southern Atlantic Ocean.<\/p>\n These transient accumulations of plastic debris near the coast pose a serious threat to marine biodiversity\u2014as highlighted by recent reports from South Africa of dead<\/a> sea turtle hatchlings<\/a> washing ashore with plastic in their guts.<\/p>\n The modeling research also indicates the possibility of a garbage patch forming in the Bay of Bengal, although more measurements of plastic concentrations are needed to confirm this.<\/p>\n The Indian Ocean\u2019s dispersed plastic debris may be more difficult to clean than waste concentrated into a garbage patch, says van der Mheen. Even so, knowing how floating debris moves through the ocean can help identify common movement pathways\u2014what she calls \u201cplastic highways\u201d\u2014where converging waste flows could one day be intercepted.<\/p>\n These results have implications for those studying plastic pollution in other oceans. Understanding the forces driving Indian Ocean plastic movement \u201cwill result in a better description of surface dispersion at the global scale,\u201d says Christophe Maes, an oceanographer at France’s Laboratoire d’Oc\u00e9anographie Physique et Spatiale.<\/p>\n