By combining the data of the total collection efficiency
(Figure 2.36) with the proportion of global plastic contained
in the NPSG (Figure 2.33) a plot of relative collection
efficiency can be obtained. This is visualized in
Figure 2.37. Here the efficiency is visualized starting from
month 26 up to month 146 (10 years) since before month
26 virtually no plastic is caught due to the “start-up” cycle
of the model.
Discussion
The model is a fit to a rather coarse data set. The Global
Drifter Program logs the positions of many thousands
of drifters in all oceans. Drifters are buoys that float in
the upper layer of the water and are moved by a sum of
influencing forces, such as wind and ocean currents. By
design, the transition matrix can only reflect the general
motion which was interpolated from the observational
data. The model relies on the following assumptions: