Microplastics floating in the North Pacific may be altering the color of the ocean, according to a study that links a measurable shift in satellite imagery to the tiny plastic particles gathering in the region. The water near the Great Pacific Garbage Patch appears to be getting brighter in the blue and green part of the spectrum, a change the researchers say natural processes alone rarely explain.
The patch sits roughly midway between Hawaii and California and covers about 1.6 million square kilometers. Estimates put the plastic debris there near 80,000 tonnes, and the density of microplastics close to the surface can reach as high as 17 milligrams per cubic liter. Much of that material is too small to see from above, which is part of why its effects on the water have been hard to track.
To look for a signal, the team analyzed three satellite datasets covering 2002 to 2022. The datasets do not fully agree on how large the change is, but they consistently show blue light rising by about 10 percent and green light by 2 to 4 percent over those two decades. The study was led by Shea Cheatham of the University of Bergen in Norway.
The researchers ran simulations comparing the effect of microplastics with natural causes such as algae blooms, which can also alter ocean color. In their models, natural changes rarely produced the blue-green brightening seen in the data. Including microplastics in the simulations made that pattern more than four times as likely, which is the central evidence the team offers.
The physics offers a plausible explanation. Microplastics scatter light strongly while absorbing little of it, which tends to brighten the blue and green wavelengths that reach a satellite sensor. Even so, Tim Smyth of the Plymouth Marine Laboratory in the United Kingdom cautioned that the connection is not yet proven. The study points to a possible satellite signature of plastic pollution rather than a direct detection of the particles themselves, and further work would be needed to confirm the cause.