MONTREAL, June 26 — Scientists have detected a natural oil leak from the seabed in the Gulf of St. Lawrence, the first such observation in these waters. According to their analysis, based on satellite images, 30,000 litres of oil flowed from an area northwest of Old Harry, a geological structure once coveted by a fossil-fuel company. The leak lasted about 50 days and was detected last summer in Québec waters.
Julien Vadnais, co-author of a study published in the scientific journal Geology, stated categorically that the researchers have not discovered an exploitable oil deposit. Nor is there any indication the leak posed an environmental risk, according to the scientists.
Vadnais, a PhD student at the University of Bergen in Norway, and his colleagues are developing “algorithms based on radar satellite data to detect natural hydrocarbon leaks at sea,” he told Le Devoir. “In August 2025, we tested our algorithms in the Gulf of St. Lawrence out of curiosity, to see what the coverage and quality of the satellite data were like. That was when a major natural oil leak was occurring.
We weren’t expecting it at all.” The flow of more than 30,000 litres was quantified thanks to a buoy collecting oceanographic data in the area. The leak occurred 35 kilometres from the Old Harry geological structure.
“The most likely hypothesis, corroborated by seismic data and the regional geological context, is that the oil escaped from a shallow accumulation after migrating from a pre-existing deposit, possibly over several kilometres,” the researchers argue, based on the data gathered on the phenomenon. The discovery raises questions about the region’s subsurface geology. Old Harry, a geological formation that once drew commercial interest, now sits near a confirmed natural seep.
The scientists were not looking for a leak when they found it — they were testing satellite data coverage. What remains to be seen is whether the algorithms developed by Vadnais and his team will detect other natural leaks in the Gulf, and what those findings might reveal about the seabed’s hidden movements.
