The Great Pacific Garbage Patch is not a solid island of trash. It is a diffuse accumulation of plastic carried by currents in the North Pacific, and its concentration of tiny fragments may be high enough to leave a faint color signature in the surrounding ocean. A ScienceAlert report by Michelle Starr describes a study suggesting that possibility, while emphasizing that the cause has not been confirmed.
Ocean optics specialists Shea Cheatham, Daniel Koestner and Børge Hamre of the University of Bergen in Norway examined how microplastics interact with light. The report says their work began with laboratory research comparing the light absorption and scattering of similar plastic fragments with those of naturally occurring seawater materials, including phytoplankton and minerals. The researchers found that microplastics could have an optical signature distinct enough to be detectable in some ocean settings.
They then used simulations to ask whether that signature might be visible to existing satellites. The simulated effect could occur at microplastic concentrations that may already be present in the Great Pacific Garbage Patch. To look for a match, the researchers examined satellite records rather than collecting new water samples.
Across three satellite datasets spanning 2002 to 2022, they identified a subtle but statistically significant brightening in blue and green wavelengths near the patch. The report describes the change as a gradually growing cyan tint. Its color pattern was consistent with the signature predicted by the simulations. That match makes microplastics a possible explanation for the observed shift, but it does not show that plastic caused it.
The proposed signal rests on how different materials affect light. According to the report, microplastics generally absorb little visible light and scatter it strongly, which can brighten the ocean in both blue and green wavelengths. Phytoplankton absorb blue and red light, while dissolved organic matter absorbs more blue; those different patterns make them less likely to produce the same combination of brightening. Mineral particles can also scatter sunlight, though the report says they are more abundant near coasts, and measurements at a nearby research station found a stable pattern of dust deposition during the study period.
Those comparisons narrow the possibilities but do not settle them. The researchers’ simulations found that some combinations of natural environmental changes could produce a similar signature, even if those scenarios were relatively rare in the simulations. And because the study relied on satellite color patterns, it did not directly measure microplastics in the water where the color shift appeared.
That missing measurement is the next step the researchers identified. Cheatham said confirming whether microplastics are responsible will require going to the garbage patch, taking optical measurements of water samples and quantifying the plastics present. Until then, the satellite pattern is a clue that could help guide investigation, rather than a confirmed way to map microplastic concentrations from space.
The question matters because the report describes microplastics as numerous but light: a 2018 survey estimated about 1.8 trillion plastic pieces in the patch, weighing around 79,000 metric tons, with microplastics accounting for an estimated 94 percent of pieces but only 8 percent of the total mass. The report also notes that cleanup efforts can remove larger debris, while the smallest fragments are difficult to remove from the water column. If the optical signal is confirmed, it could add evidence about how plastic pollution is distributed; it would not by itself solve the challenge of removing the fragments.
<a href="https://www.sciencealert.com/the-great-pacific-garbage-patch-may-be-changing-the-color-of-the-ocean">Source: ScienceAlert report</a>