Ocean plastic ‘conveyor belt’ confirmed
Expedition yacht 'Tara' is a floating laboratory
Collaborative research between two global research programs, Tara Oceans expedition 2009-2014 (France) and Malaspina 2010 expedition (Spain), has reported the large-scale transport of floating plastic debris from the Atlantic to the Arctic.
The study, published in Science Advances, highlights that within only a few decades of using plastic materials, marine plastic pollution has already become a serious problem.
The low population of the Arctic Polar Circle means little plastic waste is generated there. However, this new study shows that the Greenland and the Barents Seas (east of Greenland and north of Scandinavia) are accumulating large amounts of plastic debris that is carried there by ocean currents. Furthermore, the potential ecological implications of exposure to plastic debris are exacerbated by the uniqueness of the Arctic ecosystem.
The team behind the study, led by Professor Andrés Cózar from the University of Cadiz in Spain, is composed of 12 institutions in 8 countries: Tara Expeditions Foundation (France), King Abdullah University of Science and Technology (Saudi Arabia), Sorbonne Universités-CNRS (France), Imperial College of London (United Kingdom), Lake Basin Action Network (Japan), Universidad de las Islas Baleares-CSIC (Spain), Aarhus University (Denmark), Utrecht University (Netherlands), Harvard University (USA), IKERBASQUE (Spain) and AZTI-Marine Research (Spain).
Cózar’s research team previously demonstrated that each of the five subtropical ocean gyres act as great convergence zones for floating plastic debris. In a more recent study, they showed that semi-enclosed seas with high human density, such as the Mediterranean, can also be areas of considerable accumulation of plastic debris; however, the remote Arctic Ocean had not been considered as a candidate for accumulation.
Aboard the research vessel Tara, the team circumnavigated the Arctic ice cap and sampled microplastic over five months to complete a global map of floating plastic pollution. “The plastic concentrations in the Arctic waters were low, as we expected, but we found an area in the north of the Greenland and the Barents seas with quite high concentrations”, says Cózar. “There is continuous transport of floating litter from the North Atlantic, and the Greenland and the Barents Seas act as a dead-end for this poleward conveyor belt of plastic.”
The amount of floating plastic debris trapped in the surface waters of the Greenland and the Barents Seas is estimated to be on the order of hundreds of tons; it comprises around 300 billion pieces, mainly fragments around the size of a grain of rice. However, because surface water is not the final destination for floating plastic, the study hypothesizes that larger amounts of plastic debris exist on the seafloor beneath this Arctic sector.
Although some of the plastic found in the Arctic does come from local sources, mainly increased shipping activity in this area, the high loads of plastic in the Arctic Ocean are, in large part, due to the large-scale transportation of litter created by ocean currents from the populated coasts of the North Atlantic. This poleward transfer of floating plastic involves the Thermohaline Circulation, a global conveyor belt to date known for redistributing heat from the warmer latitudes to the poles.
To find the fate of plastic in the North Atlantic, the team used data from over 17,000 drifting satellite-tracked buoys floating on the surface of the ocean. "What is really worrisome is that we can track this plastic near Greenland and in the Barents Sea directly to the coasts of northwest Europe, the UK and the east coast of the US. It is our plastic waste that ends up there", says Dr. van Sebille from the Grantham Institute at Imperial College London.
Humans have been using plastic for only few decades, but plastic pollution in marine environments is already a global-scale problem; this is clear evidence that humans have the capacity to change our planet. “The sea has no boundaries”, explains Dr. Maria-Luiza Pedrotti of the CNRS. “Plastic trash generated in one place can pollute other, even remote areas and have devastating effects on a virgin ecosystem such as the Arctic. This region is an impasse, a dead end where marine currents deposit debris on the surface. We may be witnessing the formation of another garbage dump on the planet, without fully understanding the risks to local fauna and flora.” "The results of this study highlight the importance of minimizing plastic waste at the source. Industry, households, communities and states need to better manage their waste, because once plastic reaches the ocean, its destination and impacts become uncontrollable", says Romain Troublé, director of the Tara Expeditions Foundation.
By Jake Frith