THE SEAS OF PLASTIC

Accumulation of marine floating debris originated from highly populated coastal regions

From land to sea, contribution of coastal regions to the 5 gyres and other accumulation zones

Plastic pollution in the oceans represents a major global environmental challenge. At a global scale, man-made debris has been observed to accumulate in remote areas of the ocean in large circulating gyres. The source of this plastic is assumed to be mostly land based, however little is known about the relative contribution of different land based sources to each gyre.

By modelling and tracking the paths of plastic particles from land to sea we can estimate the relative sizes of each gyre. Also the model reveals the relative contributions of the different source regions to each of the gyres. These relationships are visualised here and allow to compare the contribtutions by source and gyre.

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KEY

Coastal Population Pressure

Plastic Particle Concentration

Dimensionless particles model: the releases and concentration are expressed in percentage of the global marine debris pollution.

Ocean Currents

Switch to
Map View Source View

KEY

Coastal Population Pressure

Plastic Particle Concentration

Dimensionless particle model: the releases and concentration are expressed in percentage of the global marine debris pollution.

Ocean Currents

Source

Numerical modelling of floating debris in the world’s oceans

Marine Pollution Bulletin, Volume 64, Issue 3, March 2012, Pages 653-661. L.C.-M. Lebreton, S.D. Greer, J.C. Borrero

A global ocean circulation model is coupled to a Lagrangian particle tracking model to simulate 30 years of input, transport and accumulation of floating debris in the world's ocean. Using both terrestrial and maritime inputs, the modelling results clearly show the formation of five accumulation zones in the subtropical latitudes of the major ocean basins.

About this project

We used large-scale hydrodynamic models to simulate global oceanic circulation. This was used to drive 'particles' released on coastal cells in the model to observe their oceanic pathways. The hydrodynamic data used was downloaded from HYCOM databases. A global human impacts study and geolocated coastal population data were used to define the density of particles released at the coast. By looping 6 years of hindcasted daily oceanic circulation, we integrated the dispersal model for a 25-year hydrodynamic simulation. Particles were released in the model domain and tracked over the 25-year simulation.

The 5 oceanic gyres are clearly visible in the results and the model has been used for extensive analysis studies identifying the relative contributions of the various sources to each gyre and other marginal seas. The relative size and concentration of each clearly illustrate the dominance of the accumulation zones in the northern hemisphere, while smaller seas surrounded by densely populated areas are also shown to have a high concentration of floating debris. We also determine the relative contribution of different source regions to the total amount of material in a particular accumulation zone. This study provides a framework for describing the transport, distribution and accumulation of floating marine debris and can be continuously updated and adapted to assess scenarios reflecting changes in the production and disposal of plastic worldwide.