Plastic litter in global oceans. Source: Cozar et al., “Plastic Accumulation in the Mediterranean Sea,” http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0121762

To better assess the severity of ocean plastic pollution, the European Space Agency (ESA) is taking a big-picture look at the issue…from space.

Considering that an estimated 10 million tonnes of plastic is dumped into the ocean each year, endangering marine life and entering the global food chain, researchers wanted to shine a light on the scale of the problem by charting where the highest concentrations of plastic pollution are found.

“Indirect measurements from space are already used to get to grips with the marine plastic litter problem," explains ESA's Paolo Corradi, who is overseeing the project.

"For instance, satellite maps of ocean currents let us simulate accumulation of litter in vast 'gyres' within the Pacific, Atlantic and Indian Oceans.

"What we are now looking at in this new project is to assess the feasibility of direct optical measurement of seaborne plastic waste from satellites. This might sound like mission impossible, but there are reasons to believe it might be indeed doable, at least for certain concentrations.

"We're not talking about actually spotting floating litter items but instead to identify a distinct spectral signature of plastic picked up from orbit, in the same way that processing software can today pick out concentrations of phytoplankton, suspended sediments and water-borne pollution.

"In particular, plastic has specific infrared fingerprints that are sometimes used in the recycling industry to sort plastic items from other refuse on a conveyor belt."

Currently, two teams (led by Argans Limited in France and Plymouth Marine Laboratory in the UK) are at work checking satellite images from missions such as the Sentinel-3 against aerial coverage and ground surveys where drifting plastic was recovered.

Paolo adds, "We hope to get an idea of what kind of concentration of marine litter is viewable from the top of the atmosphere using current technology, or if we'd have to operate from the middle of the atmosphere using aircraft or drones. Or would we have to improve the technology?"

Ultimately, the result might just be a global map showing concentrations of the waste, Paolo concluded.

"Simulations are all well and good, but an image based on actual measurements would provide important insights to scientists and would hold greater power for the public and policymakers alike.”

"Monitoring is not a goal in itself, but a means to show the scale of the problem, and start to try and solve it."

The study is published in the journal PLoS One.