Researchers use satellite infrared imagery to track oceanic plastic waste, revealing new insights into marine pollution and its sources.
A recent study conducted by the University of Cadiz and the Institute of Marine Sciences in Barcelona reveals that large floating waste rafts can be identified using standard satellite infrared imagery to pinpoint high concentrations of oceanic waste.
These drifting plastic lines, known as windrows, form where ocean currents converge at the surface and can be detected by earth observation infrared sensors on satellites such as Sentinel-2. This finding is encouraging for marine scientists, as it indicates that existing satellite technology can be utilized to study ocean pollution until a dedicated sensor system is developed.
The study sought to correlate the formation of large-scale waste rafts with the flow of terrestrial waste, which is where most ocean plastic originates. Heavy rainfall is the primary driver that pushes waste from streets into rivers and eventually into the sea. Satellite monitoring provides an “unprecedented view from source to sink” of this process.
Over six years, the team analyzed infrared imagery of the Mediterranean from the Sentinel-2 satellite, comprising 300,000 photos. The time series revealed clear instances of garbage pile formation following the rainy season, notably during three periods of extreme rainfall in 2016, 2018, and 2021. After the spring and autumn peaks, the windrows would disappear each winter, likely due to winds returning the plastic to the beaches.
The researchers identified over 14,000 waste windrows in the imagery over the six-year period. A few of these were immense, measuring 10 meters wide and up to 20 kilometers long. The northern Adriatic was found to have the highest concentration of waste windrows, making it the most polluted area due to heavy inland precipitation driving terrestrial plastic waste into runoff waters. Conversely, very little marine plastic waste was found off the coasts of Egypt and Libya, according to the study.
This research highlights the potential of using existing satellite technology to monitor and understand oceanic plastic pollution, offering critical insights that can guide future cleanup and prevention efforts.
