Arctic sea ice formation processes concentrate plastic particles into the ice. This figure shows the total number of microplastic pieces presented as values per cubic meter of seawater by polymer type, according to the location of sea ice cores.
Plastic particles are one hundred times more concentrated in Arctic sea ice cores than the most polluted parts of the north Atlantic and the great Pacific garbage patch. Processes that form sea ice scavenge plastic particles from sea water, which flows from the Pacific to the Atlantic, concentrating micro-particles of plastic and rayon in the ice in the Arctic ocean. Particle densities of 38 to 234 particles per cubic meter were found in 4 different samples taken from locations hundreds of kilometers apart. The highest particle density found to date in sea water is 0.34 particles per cubic meter in a sample taken north of Scotland in the north Atlantic. Thus,
the Arctic ocean has inadvertently become one of the world's largest plastic dumps. Scientists who tried to track plastic in the oceans knew that a large amount of plastic was missing. Now they know it is trapped in Arctic sea ice.
Update: DK user New Minas notes that the researchers used a much finer screen size to collect their samples so comparison with the great Pacific garbage patch may be comparing apples and oranges. The screen was finer by greater than a factor of 1,000. It may be impossible to compare samples from ice cores subjected to a very fine screen with samples taken from the open ocean using a relatively coarse screen.
Moreover, the source article apparently misquoted one of its references on the total volume of Arctic sea ice. The number is apparently 500 times the 2012 sea ice minimum, which is clearly not possible. Kudos to New Minas for this excellent unsolicited peer review of the source article.
end update
Polar scientists estimate that rapid warming of the Arctic is going to melt about 2,000 4 trillion cubic meters of sea ice by 2040. If the particle density is about 50 particles per cubic meter, two hundred-trillion plastic particles will go back into the water. This plastic soup will flow into the north Atlantic ocean over the next 3 decades. How this soup of plastic micro-particles will affect sea life has not yet been determined. Plastic is known to be taken up by marine organisms and birds with a variety of detrimental consequences.