Marine Debris: Modeling the Spatial Distribution of Sinking Plastics into the Deep Ocean

• Main Author: Corral, Heather
• Format: Thesis
• Language: English
• Published: 2017
• Subjects: Plastics; Marine debris; Pacific Ocean; Arctic; Arctic Ocean; Pacific; North Atlantic
• Online Access: http://hdl.handle.net/1773/39747

Four to twelve million metric tons of plastic enter the ocean each year. Although there is such a large influx of plastic entering the ocean, much of it does not remain floating at the surface. I implemented a wind-driven surface ocean circulation model (Van Sebille et al., 2012) for the top 23 sources of plastic (as identified by Jambeck et al., 2015). I initiated the model at the 23 locations simultaneously and applied a first-order degradation/sinking rate in order to evaluate both sinking and floating debris. Overall, 37% of the plastic sinks in the first year close to shore, 24% sinks on the pathway to ocean gyres, and 39% of the plastic sinks once it is in a gyre. Selected sources were further evaluated including New York, and the four sources that feed into the Mediterranean Sea: Algeria, Turkey, Egypt, and Tunisia. Plastic pollutants sourced from New York traveled across the North Atlantic Ocean with some traveling up into the Arctic ocean and some circulating back into the Caribbean. With an average of 0.075 MMT leaving New York, approximately 0.028 million metric tons (MMT) sunk at the coast of the United States prior to crossing the Atlantic, 0.018 MMT sunk on the path between the coast of New York and the journey to the Arctic Ocean, and 0.029 MMT sunk from the surface once it reached its destination. A similar situation occurred in the Mediterranean Sea. 0.61 MMT of plastic is released to the Mediterranean each year. With my locations being on the southern shore of the Mediterranean Sea, the plastic traveled North over time. 37%, which calculates to 0.23 MMT, sank close to the initial location. 0.15 MMT of plastic sunk before traveling Northeast or Northwest (depending on site), and 0.24 MMT sunk from the surface once reaching the Northern shores of the Mediterranean Sea. Finally, it is interesting to note that none of the 23 largest sources of plastic source into the Southern Pacific Ocean directly.