As part of The Ocean Cleanup Project’s mission to clean the Great Pacific Garbage Patch several of their researchers have for the last five years been working to understand both the scope of plastic pollution but also from where and when it originates. As part of this they estimated in 2018 that there were in the vicinity of 80,000 tons of plastic currently trapped in the Great Pacific Garbage Patch. However, these figures stand in contrast of the several million tons of plastic that other scientist estimate enters the oceans every year. A study by Snorkels and Fins estimate that in the near future plastic will outweigh fish in the oceans. This begs the question of where the remaining plastic is.
The common explanation is partly that a lot of the plastic breaks down into micro plastic, floating underneath the surface of the ocean, sometimes called the plastic smog. This micro plastic is what often ends up deeply embedded in the various underwater food-chains and even in acrtic snow.
However, this does not solve the puzzle of why there is not more plastic of recent origin. To get a better view on how old plastic in the Great Pacific Garbage Patch actually is The Ocean Cleanup Project went through the over 80,000 plastic items they collected and found 50 pieces with manufacturing dates on them.
While the sample size is relatively small this does exemplify that there is something missing from the current picture. The Ocean Cleanup Project’s simulation shows that a significant portion of the plastic emitted from rivers and likely return back to shore within a short time frame. Another large chunk of the plastic is send back to shore due to waves and tidal movements The result is a substantial delay between when plastic enters the ocean for the first time and when it actually ends up in the Great Pacific Garbage Patch.
While there are multiple implications of this, one of the more troublesome ones is that this indicates that the current micro plastic we observe in the oceans are likely from plastic that was discarded years or even decades ago. As plastic pollution has continued to increase this time lag implies that even if we were to drastically reduce current levels of plastic pollution a large stock of plastic will continue to break down and pollute the oceanic ecosystem.