Ocean Sciences News

Pacific’s Garbage Hot Spot Holds More Plastic Debris Than Was Thought

A nonprofit that helped to collect data for the research plans to use the study’s findings to help guide it in an upcoming campaign to remove buoyant plastic trash from ocean gyres.

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The sprawling Great Pacific Garbage Patch (GPGP) not only is the largest plastic accumulation zone on Earth but also is contaminated with 4–16 times more floating plastic by mass than previously estimated, according to a paper published today in Nature Scientific Reports. The 1.6-million-square-kilometer garbage patch, located in the eastern part of the North Pacific Subtropical Gyre between Hawaii and California, contains at least 79,000 metric tons and an estimated 1.8 trillion pieces of floating ocean plastic, the paper reports.

The garbage patch covers about 3 times the area of continental France and encloses buoyant plastic tonnage equivalent to 500 jumbo jets, according to the Ocean Cleanup Foundation. This nonprofit organization, headquartered in Delft, Netherlands, supported the study by providing data from two major expeditions: a 2015 “Mega Expedition” during which 30 vessels crossed the garbage patch to map it and a 2016 aerial expedition. The study was authored by scientists affiliated with the foundation, six universities, and an aerial sensor company.

The 3-year research effort, which investigated the area from ships and aircraft, found that debris larger than 5 centimeters makes up more than 75% of the GPGP plastic mass, with much of that being fishing nets. Measurable pieces of microplastic less than 4 millimeters in size account for 8% of the mass.

Many Factors Behind Debris Increase

Prior estimates by other researchers have put the plastic tonnage adrift in the patch between about 4,800 and 21,000 metric tons. The new paper suggests that the increased estimate of floating plastic mass is due mainly to more robust methods for quantifying ocean debris. However, increased levels of plastic pollution in the area—including plastic from the 2011 Tohoku tsunami—could also account for some of the difference, the authors note.

Despite the enormous amount of floating plastic, the study found that it’s far less than global models had predicted based on plastic inputs from land- and marine-based sources. The researchers conclude that other dispersal—including through beaching and fragmentation into ever-smaller and unmeasured pieces—accounts for some of the shortfall compared to model predictions. Moreover, “levels of plastic pollution in deep water layers and [on the] seafloor below the GPGP remain unknown and could not be quantified through sampling,” the paper states.

The Ocean Cleanup Foundation, which has an ambitious goal of cleaning up 90% of all ocean gyres by 2040, plans to take cues from the study’s results as it develops a fleet of passive floating collection devices. The group plans to deploy its first cleanup system in mid-2018. Foundation founder and CEO Boyan Slat said that the study results “provide us with key data to develop and test our cleanup technology, but it also underlines the urgency of dealing with the plastic pollution problem.”

—Randy Showstack (@RandyShowstack), Staff Writer

Citation: Showstack, R. (2018), Pacific’s garbage hot spot holds more plastic debris than thought, Eos, 99, https://doi.org/10.1029/2018EO095345. Published on 22 March 2018.
© 2018. The authors. CC BY-NC-ND 3.0