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Satellites detect a brightening around the Great Pacific Garbage Patch
Around the Great Pacific Garbage Patch (GPGP) in the North Pacific, the colour of the sea is changing. Twenty years’ worth of satellite data show a measurable brightening in the blue and green spectrum of light; the water is taking on a slight cyan hue.
A team of researchers from the University of Bergen sees this development as a possible indication of large quantities of tiny plastic particles floating in the water. The study by Shea Cheatham, Daniel Koestner and Børge Hamre was published on 5 November 2026 in the journal Communications Earth & Environment. However, the authors themselves emphasise that it does not provide proof that microplastics are the cause.
The GPGP is not a solid island of rubbish, but an area where ocean currents cause plastic to accumulate. A 2018 estimate put the figure at around 1.8 trillion pieces of plastic with a total weight of approximately 79,000 tonnes. For researchers, the problem lies with the smallest particles: methods used to detect floating rubbish from space rely on infrared light and are not suitable for tiny particles suspended below the surface. The authors therefore took a different approach and searched for traces of the particles in the colour of the ocean.
Sea colour measured via satellite
The team analysed three satellite datasets on sea colour (MODIS, GlobColour and OC-CCI), covering the period from August 2002 to September 2022. They investigated how much light the water reflects across different colour bands. In all three datasets, a statistically significant increase in both the blue and green spectral bands is evident within and near the GPGP, resulting in a cyan hue. It is already known from previous studies that the sea in the North Pacific is becoming brighter in places. What is striking here is the combination of blue and green.
The datasets do not agree in every detail. The researchers attribute this primarily to sensor drift in the MODIS instrument in later years and to differences in calculation methods. The dataset from the ESA’s OC-CCI climate initiative provides the most conservative figures, but also shows blue-green areas where microplastics are likely to accumulate.
Members of the team had previously investigated in the laboratory whether microplastics can leave any traces in the colour of the sea at all. Plastic particles absorb very little visible light and reflect it strongly. Plankton, on the other hand, selectively absorbs certain colours, thereby shaping the typical colouration of seawater. If there is a lot of plastic floating in the water, the water therefore becomes brighter, most noticeably at a wavelength of 490 nanometres, in the transition from blue to green.
How robust is this theory?
To test whether microplastics could explain the brightening, the team ran computer simulations of how light travels through the atmosphere and the water, using nutrient-poor water such as that found in the North Pacific. According to these simulations, once concentrations reach around five milligrams of microplastics per cubic metre of water, the brightening at 490 nanometres exceeds the normal variation in satellite measurements. By way of comparison: based on net catches from 2016, the authors estimate the peak concentrations of larger microplastic particles (0.5 to 5 millimetres) in the near-surface waters of the GPGP to be more than 17 milligrams per cubic metre. According to a 2025 Nature study, the average concentration of nanoplastics in the upper water layer of the North Atlantic is around 15 milligrams. However, concentrations of particularly small particles under 0.3 millimetres have not yet been measured directly in the GPGP.
If the entire brightening were attributable solely to plastic, the concentration in the most severely affected grid cell would have had to have risen by between 11 and 25 milligrams per cubic metre, depending on the dataset. The authors consider this to be a realistic order of magnitude.
A second test consisted of 500 simulated scenarios in which plankton composition, dissolved organic matter and natural suspended particles varied, once with and once without microplastics. Without plastics, only 3 per cent of the simulated cases of brightening resulted in a cyan hue, and even then only in the case of significant changes, such as a complete shift towards smaller plankton species and, in most cases, lower biomass. With microplastics as an additional variable, the proportion rose to 13 per cent – more than four times as high. This is a result derived from simulations and not a value measured in nature.
The authors have not ruled out natural causes. They even consider it conceivable that moderate changes in the ecosystem and microplastics could jointly contribute to the brightening. Nor do they rule out disruption to the ecosystem caused by chemicals adhering to plastic. By contrast, they consider calcareous algae (coccolithophores) and mineral dust to be unlikely explanations: measurements of dust deposition at the Aloha research station near Hawaii show no noticeable change between 1980 and 2025.
What is lacking is on-site measurement. According to the authors, water samples and optical measurements within the water column at the GPGP itself are needed to verify the findings.
If the link is confirmed, this would initially have implications for research. The colour pattern – a simultaneous brightening in blue and green – could, in the authors’ view, serve as a diagnostic tool for estimating microplastics from satellite data. So far, such particles can only be detected through labour-intensive on-site sampling, which is difficult to extrapolate to large areas. Satellites, by contrast, cover large areas over decades. Clear evidence of the extent of microscopic pollution is important in order to tackle the growing use and mismanagement of plastic, the authors write.
Microparticles probably cannot be removed…
The second implication concerns clean-up efforts. Projects aimed at removing plastic from the sea retrieve larger pieces from the water. According to the authors’ assessment, the tiny particles smaller than 0.3 millimetres can hardly be removed on a large scale, if at all. At the same time, new ones are constantly being created as larger pieces of plastic in the water break down due to sunlight and mechanical stress. According to ScienceAlert, Cheatham therefore sees only one effective solution: plastic must not be allowed to enter the water in the first place.
Added to this is the food chain. According to the authors, the small microplastic particles are most likely to end up in the lowest level of the marine food web. There, they can accumulate and, via seafood, also reach humans. The authors also point out that microplastics affect ecosystems and the carbon cycle. The extent to which the plastic in the GPGP influences the ocean’s ecology remains to be clarified.
It also remains unclear what this means for the satellite measurements themselves. Satellites typically use the ratio of blue to green to calculate the amount of chlorophyll – and thus the amount of plankton – in the water. The authors note that the effects of dissolved substances, suspended particles and chlorophyll on ocean colour are, in any case, difficult to distinguish from one another. The study does not investigate whether additional plastic could distort such plankton estimates. That would be an obvious question for follow-up research.
Whether the Pacific is actually becoming brighter due to plastic can only be clarified by measurements taken within the garbage patch itself. Until then, the study provides a reasonable indication but does not yet constitute proof.
More information:
Cheatham, S., Koestner, D. & Hamre, B.: The ocean's color is changing near the Great Pacific Garbage Patch. Communications Earth & Environment 7, 855 (2026)
ScienceAlert: The Great Pacific Garbage Patch May Be Changing The Color of The Ocean
Koestner, D. et al.: Measurements of the inherent optical properties of aqueous suspensions of microplastics. Limnology and Oceanography Letters (2024)
ten Hietbrink, S. et al.: Nanoplastic concentrations across the North Atlantic. Nature 643 (2025)