At the beginning of August, an expedition team led by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) will be travelling to the Mackenzie Delta in north-western Canada – an area that has warmed by 0.3 degrees Celsius per decade since 1940. There, the researchers want to investigate the danger posed by more than 200 drilling mud pits. TU Braunschweig, Leibniz Universität Hannover and RWTH Aachen University are also involved in the ThinIce research project. The research team is working closely with Canadian scientists, regional authorities and the provincial administration of the Inuvialuit communities.

"Between the 1970s and 1990s, around 230 pits were dug in the Mackenzie Delta to dispose of mud that was produced during drilling for oil and gas," explains AWI researcher Dr Moritz Langer from the Permafrost Department, who is leading the project. The 100 to 200 meters mud pools were then filled with sediment, so that today the tundra is traversed by a number of small mounds. However, a toxic mixture lies beneath them: "In addition to sediment and rock, the mud also contains fluids rich in salt or paraffin, which companies have used as anti-freezing compounds in the drilling process. The latter in particular are environmentally critical because they are poorly degraded by microorganisms in the soil," says Langer.

Similar to the Mackenzie Delta, there is only incomplete or hardly any publicly accessible data for many industrial sites and activities in the Arctic, which makes risk assessment difficult. "This makes it all the more urgent that we get an overview of the nature and extent of the contaminated sites and develop concepts for securing and remediating them," says Langer. This is also because the renaturalization of contaminated areas becomes increasingly expensive the deeper the permafrost thaws, or even impossible if heavy machinery can no longer be used on the unstable soils.

On the upcoming expedition in north-west Canada, the research team will initially investigate the drilling mud pits in a relatively large area that encompasses various ecosystems. Soil and water samples will be taken in the vicinity of the drilling mud pits in order to analyze them for pollutants. In addition, hydrological and thermal soil measurements will be carried out and the drilling mud pits will be surveyed in detail using drones. In 2025, further expeditions will then take targeted samples at selected locations. The results from the project will serve as a basis for working with local partners to develop strategies to minimize the risk of leaking contaminated drilling fluids.

The team posts regular updates and photos of the field research online on the ThinIce website.