Microplastics in the Arctic Ocean brought in by European rivers | Polarjournal
You can’t see it in the ocean or sea ice, but microplastics are found everywhere in the Arctic. Photo: Julia Hager

Since the start of plastic production in the 1950s, environmental input of plastic is so massive that is found in every habitat on earth: in the deep sea, on Mount Everest and in the ice of the polar regions. This is especially true for microplastic particles. The Arctic Ocean is also heavily polluted with microplastic particles. However, scientists have been puzzling over their origin until now. As part of a new study published in the Nature journal Scientific Reports, a Norwegian research team has now been able to use models to trace the pathways of floating microplastics.

Microplastics are plastic particles up to five millimeters in size. Primary sources of microplastics include industry, households (clothing fibers, cosmetics etc) and road traffic (tire and brake abrasion). However, the tiny particles are also formed when larger plastic particles break down due to environmental influences such as sunlight and salt water. They are then distributed over the entire planet via rivers and the atmosphere.

Humans and animals absorb microplastics through food or air. For animals, ingestion has been shown to be harmful or even fatal. Little is still known about the health consequences for humans.

Arctic ocean currents and European rivers as sources of microplastics releasing more than one ton of microplastics per year into the open sea, sorted by magnitude of microplastic input: A-Ob, B-Rhine, C-Vistula, D-Jenissei, E-Oder, F-Elbe, G-Neman, H-Weser, I-Seine, J-Daugava, K-Themse, L-Neva, M-Meuse, N-Trent, O-Dvina, P-Ems, Q-Pregolya, R-Scheldt, S-Lielupe, T-Mersey, U-Severn. Map: Huserbråten et al. 2022

In the Arctic, a previous study found up to 166 microplastic particles per cubic meter of water in the Greenland Sea between northeast Greenland and Svalbard. However, the route by which the particles enter the Arctic Ocean was not known until now. In the current study, the team, led by Mats Huserbråten of the Institute of Marine Research, in Bergen, Norway, used models to determine how microplastic particles floating on the water surface in the Arctic Ocean, Nordic adjacent seas and Baffin Bay spread from Europe.

Using the models, the scientists were able to predict how many microplastic particles are found in specific regions of the Arctic Ocean over a period of several decades. After comparing their calculations with water samples from these areas, they concluded that microplastics must have been circulating in the Arctic for at least ten years.

To track the path of particles in the Arctic Ocean, the researchers combined ocean current models from 2007 to 2017 with simulations of the transport of floating microplastics. They then simulated the release of microplastics from 21 major rivers in northern Europe and the Arctic per day over a ten-year period.
They also compared the results of their model to the distribution of floating microplastics from 121 seawater samples the researchers collected off the west coast of Norway in 2017 and 2018.

The main drift pathways of floating microplastics through the Arctic Ocean. Microplastic particles from the Rhine (dark blue lines) — the largest source of microplastics from rivers in Northern Europe — were used as an example. Alternative paths run along the West Spitsbergen Current (orange lines) or recirculate in the Arctic adjacent seas (yellow lines). Probably the largest source in the Arctic Ocean is the Ob River (purple lines). The dark blue dots mark the sampling points of the seawater samples. Map: Huserbråten et al. 2022

They found that most of the simulated microplastic particles follow two main pathways after their release from rivers. At least 65% of the particles drifted eastward along the Norwegian coast into the Laptev Sea, from where they entered the Arctic Ocean, drifted over the North Pole, and finally drifted southward into the Atlantic Ocean via Fram Strait between northeast Greenland and Svalbard.

About 30% of the particles followed the continental shelf from northern Norway to the west coast of Spitsbergen. A little further north in Fram Strait they caught the southward flow described above, with which they moved together with the particles transported over the North Pole along the east coast of Greenland into the Labrador Sea and further south to the Canadian coast.

Left: Frequency of floating microplastics. The simulations resulted in five accumulation zones: I – Nordic waters, II – Barents Sea, III – Nansen Basin, IV – Laptev Sea shelf edge, V – Baffin Bay. Right: Estimated duration of transport of floating microplastics from the North Sea to the Arctic Ocean and its marginal seas in years. Map: Huserbråten et al. 2022

In addition, the research team determined that particles originating from the heavily polluted industrial regions of the North Sea reach the Norwegian Sea in less than two years. After four to six years, they have reached as far as the Eurasian part of the Arctic Ocean, and after up to ten years, they have reached the north coast of Canada.

The authors conclude that the plastic particles appear to remain in the surface layer of the Arctic Ocean for a very long time – up to decades – which may have far-reaching consequences for Arctic ecosystems. Invertebrates, fish, birds and mammals can ingest the particles, which can cause many different harmful physiological reactions. They see better waste management that reduces the potential for microplastics to spread from land to the oceans as urgently needed.

Julia Hager, PolarJournal

Link to the study: Huserbråten, M.B.O., Hattermann, T., Broms, C. et al. Trans-polar drift-pathways of riverine European microplastic. Sci Rep 12, 3016 (2022). https://doi.org/10.1038/s41598-022-07080-z

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