The waters around the Great Pacific Garbage Patch have become lighter in the blue and green spectra over the past two decades. Scientists from the University of Bergen are investigating whether the accumulation of microplastics plays a role in this change by analyzing three separate 20-year sets of satellite data covering the period from 2002 to 2022.
The change was detected in and around the area of plastic accumulation, while the same pattern was not observed in waters farther away. According to the researchers, satellite images alone cannot prove that microplastics are the main cause of the brightening.
“Observing a spectral increase in brightness that coincides with the modeled increase in the concentration of microplastics in the water does not, by itself, show that microplastics are the main cause of the observed increase in brightness,” the study’s authors note.
What the models show
Computer simulations, however, support a possible causal link. In them, microplastics scatter light in a way that creates a brightening pattern similar to that observed by satellites.
A similar result is obtained in 3 percent of simulations when only natural changes are included. In models that also include microplastics, the share of such results rises to 13 percent. The study notes that changes in the amount of plankton or organic matter could theoretically have a similar effect, but this would require unusually large ecological changes to have occurred.
Ocean color depends on the light reflected by substances in the water, including plankton, organic matter and particles. Microplastics can enter the sea as larger waste breaks down or can be produced directly in microscopic sizes.
Possibility of monitoring from space
If microplastics are confirmed to contribute to the observed change, satellite measurements of ocean color could become a tool for tracking pollution from space. This would be important because the particles are extremely difficult to detect and collect on a large scale.
Microplastics can be as small as a fraction of a micrometer. Unlike large floating debris, they are not easily visible from a distance, and conventional satellite infrared instruments have difficulty detecting them.
The study was published in the journal Communications Earth & Environment. The authors point out that additional measurements taken directly in the water are needed to determine whether the satellite-observed brightening is indeed linked to the accumulation of microplastics.