A wide stretch of the North Pacific between Hawaii and California has grown brighter in both blue and green light over two decades, and a new study suggests microplastics drifting in the Great Pacific Garbage Patch may be part of the reason. The research, published Nov. 5 in Communications Earth & Environment, has not proved that plastic is changing the color of the sea, and its authors say so plainly.

If the link holds up, it would matter well beyond one patch of ocean. The smallest microplastics are notoriously hard to count from ships, and a satellite method could one day show where they collect, how fast concentrations are rising and whether cleanup or prevention efforts are working.

For readers on the West Coast and in Hawaii, the patch is not an abstraction. It sits in the North Pacific gyre that shapes the waters off California, and earlier research traced much of its larger debris, especially fishing gear, to fishing industries in several countries, including the United States, ScienceAlert reported.

Reading the Ocean's Color From Orbit

Ocean color is measured by satellite sensors that record how much sunlight bounces back from the upper layer of the sea at different wavelengths. Clear open ocean looks blue because water absorbs red light and scatters blue. Anything floating in that top layer, from microscopic algae to sediment, shifts that balance recognizably.

The study team, ocean optics researchers Shea Cheatham, Daniel Koestner and Børge Hamre of the University of Bergen in Norway, began in the lab. They measured how microplastics absorb and scatter light compared with phytoplankton, minerals and dissolved organic matter.

They found that microplastics absorb very little visible light but scatter it, brightening the water at blue and green wavelengths at the same time. Phytoplankton behave differently, absorbing blue and red light and leaving the sea looking greener. Dissolved organic matter absorbs more blue, making water look darker or browner.

The team then searched three long-running satellite records covering 2002 to 2022, including the MODIS instrument on NASA's Aqua satellite and two products that merge data from multiple satellites, according to IFLScience. All three showed areas in and around the patch growing brighter in blue and green, a slowly building cyan tint.

A Blue-and-Green Brightening Few Natural Causes Explain

That simultaneous brightening is the unusual part — natural changes rarely lift both colors together. To test explanations, the researchers ran hundreds of computer simulations of changing seawater. When microplastics were excluded, only about 3% of runs reproduced the cyan shift. When microplastics were included, about 13% did.

The authors read that result cautiously, describing a plausible scenario in which moderate ecosystem changes and accumulating microplastics both contribute. In other words, plastic is not presented as the only driver.

They also checked for mineral dust, which can brighten the ocean. Dust is more common near coasts, and a nearby research station recorded stable dust deposition during the study period.

Cheatham described the team's reaction to the first dataset. "We were shocked, excited, and a little alarmed to see the same shift in ocean color on the map," she told ScienceAlert.

The scale of the patch helps explain the concern. A 2018 survey estimated about 1.8 trillion plastic pieces weighing roughly 79,000 metric tons in an area about twice the size of Texas. Microplastics made up about 94% of the pieces but only about 8% of the mass.

Skeptics Point to Sensor Drift and Plankton

Outside scientists are divided. Anna Sànchez-Vidal of the University of Barcelona called the work original but said the approach is not yet ready for routine use and must be validated with field campaigns paired with satellite passes, according to reactions gathered by the Science Media Centre Spain. She noted that coastal waters such as the Mediterranean are optically more complex and would need separate testing.

Andrés Cózar of the University of Cádiz was more critical. He said he was "not convinced by the study," arguing that it shows a statistical correlation rather than direct evidence of plastic.

Cózar raised several alternative explanations for the trend: gradual drift in satellite sensors over two decades, errors in the atmospheric corrections used to process the images, and shifts in the types of phytoplankton living in the gyre. He also questioned whether microplastic concentrations are high enough to register with the relatively coarse-resolution sensors used.

Those concerns go to the core of the claim. Long satellite records — some spanning several instruments — are stitched together from sensors that age and are recalibrated, and the open Pacific is also changing for reasons unrelated to plastic, including warming. Cheatham has said more research is needed to determine whether the color change is directly and exclusively caused by plastics.

A Sampling Voyage and a Possible Monitoring Tool

The decisive test has to happen at sea. The team plans to collect water in the patch, measure its optical properties and count the microplastics present. "We will need to go to the garbage patch to make optical measurements of water samples," Cheatham said, adding that the group is hopeful a voyage can happen in the future. No date has been announced.

Study type matters here. This is peer-reviewed work combining laboratory optics, simulations and observational satellite data. It found a color trend consistent with microplastics; it did not measure plastic in the water or establish cause and effect. It covers one region and two decades, and it does not change any public health or seafood guidance.

For households, the practical takeaways are modest but real. Microplastics in the patch largely come from larger debris breaking apart, so reducing single-use plastic and properly disposing of fishing line and gear remain the most direct personal steps. Readers should be wary of products that claim to remove all microplastics without independent certification.

The bottom line is that satellites have recorded a genuine two-decade cyan shift over the Great Pacific Garbage Patch, and microplastics are a plausible but unconfirmed contributor. Water samples from the patch will decide whether ocean color can become a tool for tracking plastic pollution from space.

What Readers Want to Know

What did the study find?

Satellite records from 2002 to 2022 show parts of the Great Pacific Garbage Patch brightening in both blue and green light, a shift consistent with the optical signature of microplastics.

Does this prove plastic is changing the ocean's color?

No. The authors say direct water sampling is still needed, and outside experts say sensor drift or changes in phytoplankton could also explain the trend.

Where is the Great Pacific Garbage Patch?

It lies in the North Pacific gyre between Hawaii and California, where currents trap floating debris.

Why does a blue-and-green brightening point to plastic?

Microplastics mostly scatter light and brighten both colors together, while phytoplankton and dissolved organic matter tend to shift water greener or darker.

Could satellites track microplastics in other oceans?

Possibly, if the method is confirmed. Experts say complex coastal waters would need separate testing.

What happens next?

The University of Bergen team plans to sample water in the patch and measure its optical properties. No expedition date has been announced.