Majority of the world’s oil slicks caused by human activity

Oil slicks are microscopically thin layers of oil that float on the surface of the ocean and are a form of marine pollution. They are the result of oil spills from ships or oil and gas platforms, and from natural seeps that occur at the bottom of the ocean. Oil slicks also emerge when industrial runoff is channeled to the sea. In previous research, around 50 percent of ocean oil slicks were said to be attributable to human activities, but new research has found that this is an underestimate. 

A team of U.S. and Chinese scientists has used satellite imagery to map oil pollution across the Earth’s oceans. Since oil slicks are continuously being shifted around by winds and currents, and broken up by wave action, it is not easy to identify their source or origin. The scientists used artificial intelligence to examine more than 560,000 satellite radar images collected between 2014 and 2019 to determine the location, extent and probable sources of the ocean’s oil slicks. 

Their findings, published today in the journal Science, indicate that up to 90 percent of the oil slicks in the ocean derive from human activities. Study co-author Ian MacDonald is a professor in the Department of Earth, Ocean and Atmospheric Science at Florida State University.

“What’s compelling about these results is just how frequently we detected these floating oil slicks – from small releases, from ships, from pipelines, from natural sources such as seeps in the ocean floor and then also from areas where industry or populations are producing runoff that contains floating oil,” said Professor MacDonald.

Oil slicks are dangerous for marine life, from large mammals like whales down to microscopic plankton. Air-breathing organisms such as whales, porpoises and turtles can be affected when they surface in the oil and attempt to breathe. Sea birds get coated in oil and are unable to swim or forage, which leads to their rapid demise. For these reasons, it is imperative to be able to monitor the extent of oil spills in the ocean and try to limit their effects.

“Satellite technology offers a way to better monitor ocean oil pollution, especially in waters where human surveillance is difficult,” said study co-author Professor Yongxue Liu of Nanjing University. “A global picture can help focus regulation and enforcement to reduce oil pollution.”

Using this technology, the researchers found that most oil slicks occur close to the coast. About half of them were located within 25 miles of the coast, and 90 percent were within 100 miles. This indicates an anthropogenic origin for most of them. 

Interestingly, the researchers found relatively fewer oil slicks in the Gulf of Mexico compared to elsewhere on the globe, suggesting that government regulation and enforcement, as well as compliance from oil platform operators in U.S. waters, reduces leakage.

“If we can take those lessons and apply them to places globally, where we have seen high concentrations of oil slicks, we could improve the situation,” MacDonald said.

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By Alison Bosman, Earth.com Staff Writer