Last winter, inside the subarctic Churchill Marine Observatory in Canada, scientists embarked on an experiment they hoped would result in a gamechanging remedy for polluted Arctic waters. They released 130 litres of diesel into an ice-covered pool filled with raw seawater pumped in from Hudson Bay and added oil-eating microbes. The technique had been used successfully during the Deepwater Horizon oil spill in the Gulf of Mexico, and the scientists wanted to see if they could break down oil in colder waters.

The microbes were sluggish in response and the population showed little change after the first three weeks, says Eric Collins, a microbiologist at the University of Manitoba in Winnipeg, who led the project. But that did not last. “When we went back eight weeks later, we saw that there was a big change,” Collins says. “One particular bacterium grew to a very high abundance in the tanks and it was clear that it was feeding on the oil.” But two months is too long to wait should an oil spill occur. Time is of the essence.

At least 100 shadow fleet ships travelled along Russia’s northern sea route last year. These are often ageing, unregulated vessels secretly transporting oil that has been placed under sanctions around the world. Just thirteen shadow fleet vessels made the journey in 2024, and none in 2023, according to data collected by the Bellona Foundation, a Norwegian nonprofit. In 2025, more than half were oil and liquefied natural gas tankers, 18 of which had low or no ice class, meaning they were not designed to operate in icy waters.

This heightens the risk of an ecological disaster in one of the most fragile environments on Earth. Few techniques exist to clean up oil from Arctic waters, despite millions of dollars of investment into research.

“[The shadow fleet] adds a huge unknown – where are these ships, where are they travelling to, what cargoes are they carrying? It escalates the risk,” says Sian Prior, lead adviser to the Clean Arctic Alliance, a group of 24 nonprofits working to protect the Arctic from the impact of shipping.

Polar observers have long forecast a steady rise in Arctic shipping as sea ice melts, but the sudden emergence of the shadow fleet on the northern sea route was unexpected, experts said. Arctic oil spill cleanup methods have not kept pace.

Ksenia Vakhrusheva, the Bellona Foundation’s Arctic project manager, says: “They are usually tankers meant for scrap, but the previous owners didn’t want to pay for scrapping so they just sold the ships elsewhere. These types of vessels are the most concerning if they go along the northern sea route, because even if they come across light ice or some floating ice formations, it can be dangerous.”

The growing threat of a large-scale spill in Arctic waters is a challenge for scientists. Oil behaves differently in the Arctic compared with warmer seas. Cold temperatures make some fuel types more viscous, and they form molasses-like globules that can sink to the bottom to mix with sediment or stick on to ice. Sea ice interferes with the boats’ skimmers and booms used to scrub oil from the surface. And pumping and transfer methods struggle because the oil is thicker.

Synnøve Lofthus, a senior adviser on oil spill protection and environmental preparedness with the Norwegian Coastal Administration, says: “One of the core challenges with oil spill response in the Arctic is that it is the Arctic. If something happens, it’s very hard to get there and do something about it.”

Millions of dollars have gone into programmes over the past 15 years to uncover new technologies and techniques for rapid Arctic oil spill cleanup. But little has materialised. In 2012, fossil fuel companies provided $20m (£15m) to form the Arctic Oil Spill Response Technology Joint Industry Programme (JIP). The programme ended in 2017 and conceded in its synthesis report: “Substantial improvements in mechanical recovery efficiency could not be readily achieved by new equipment designs.”

Instead, the JIP focused on the use of dispersants – chemical agents that break slicks into smaller particles in the water column – and in situ burning to remove oil. Dispersants can be hazardous, says Lofthus, adding: “If you put oil into the water column along the ice edge or in the marginal ice zone, when it is high primary production, you might really affect the organisms there in their early sensitive life stages.” And although burning can work well in the Arctic where ignitable gases are slower to evaporate, it produces black carbon that can speed up ice melting.

Others have sought gentler remedies, such as the Churchill Marine Observatory’s efforts to introduce the oil-eating microbes to slicks.

Ultimately, though, no new solutions have materialised, says Prior. “The [cleanup] technology that is available today is much the same as it was 10 or 15 years ago,” she says. “There’s nothing new that’s come on to the market. What is new is that these fuels have changed.”

In 2020, the International Maritime Organization introduced a sulphur cap on marine fuels to help reduce shipping emissions. It had the unintended consequence of ships adopting new fuels that were even more challenging to clean up.

Lofthus, who also serves as co-chair of the Arctic Council’s Arctic Oil Spill research and development initiative, says these low-sulphur fuels are often blended with paraffins. “So now you have a type of oil that either forms lumps, or a lot of them have this weird viscoelastic property that makes it even harder to recover.”

Shadow fleet vessels on the northern sea route, she adds, may still be using heavy fuel oil, but ships use whatever fuel is cheapest on the market when they are filling up, bringing yet another layer of risk to Arctic waters.

Beyond Russia, Arctic infrastructure development and the growing militarisation of the region have served as an impetus for investing more in oil spill research. Collins’ work was funded through money from the Canadian government. Mark Carney, the prime minister, recently proposed revitalising a deepwater port in Churchill that would provide a connection to the North Atlantic.

Collins says: “It’s no coincidence. There has been a lot of focus on Churchill. That’s partly why the [Marine Observatory] is there, because of this idea that it may be a bigger port in the future and we should be doing this kind of research.”