A study examining satellite data from 2023 to 2026 found that more than 90% of detected oil pollution was concentrated in seas within countries’ jurisdictions, particularly near coastlines. Much of the open sea is not imaged frequently enough, however, so the actual extent may be greater than the recorded picture suggests.
Researchers used radar images from the European Space Agency’s Sentinel-1 satellites. The system can capture data at night and through cloud cover, allowing oil slicks on the sea surface to be tracked. They compared the satellite images with AIS vessel-position data to identify likely sources of the pollution.
Of the annual area of oil slicks for which a source could be identified, about 81% was attributed to ships. Cargo vessels and tankers were particularly prominent. Concentrated slicks were detected in the Red Sea, Persian Gulf, Mediterranean and Black seas, off the coast of West Africa, and in waters around Indonesia.
The findings indicate that marine oil pollution is not limited to major accidents. Sixteen ships were linked to oil leaks on multiple dates. In more than 10% of satellite images involving those vessels, slicks appeared nearby or behind them. Repeated pollution traces were also found around some oil facilities off Indonesia and Nigeria.
Oil traces appeared in protected waters as well, including habitats of dolphins and whales in the Black Sea and areas of the Gulf of Mexico where the critically endangered Rice’s whale lives. Researchers caution that the 1.58 million square kilometres covered by the analysis may not capture all pollution: many slicks could have gone unnoticed in areas that satellites observe less often.