A brutal field trip gave researchers new insight into Arctic winters

“We completely underestimated the trip, especially with the amount of equipment we had to carry. Sleep was also in short supply and people were exhausted,” says Professor Willem van der Bilt of the University of Bergen and the Bjerknes Centre.

He is reflecting on the demanding field trip to northern Svalbard in the summer of 2022.

The researchers spent more than 24 hours in the field and returned to the boat with sediment samples from Lake Stuptjørna. In total, they walked 9 kilometres with an elevation difference of 400 meters, carrying heavy equipment.

And Stuptjørna lived up to its name. The terrain was steep and at times almost impassable.

The white spot in the distance

Alexandra Rouillard from Umeå University was also part of the team. It was her first trip to Svalbard. 

What began as a scenic hike turned into a demanding expedition across steep terrain, unstable boulder fields, and long ascents with heavy equipment – all while constantly being aware that polar bears roam the area.

“I seriously began questioning my priorities in life. At one point, staying alive felt like a strong contender to science,” she says.

After more than 24 hours, they returned to the shore of Wijdefjorden with their sediment cores and wet gear.

“We all took a much-needed cleansing swim and finally made it back to the sailboat, ferrying our equipment and people back and forth until the last of the team were on board. Pure joy. Minutes later, we noticed a white spot on the beach we just left behind,” Rouillard says. 

In the picture below you can see what that was.

Minerals formed under special conditions

The lake was chosen because of its high elevation. The goal was to gain a better understanding of past Arctic winter climate and the natural mechanisms that control it, by using this lake as an archive of winter conditions.

“The higher the lake, the longer winter lasts,” says van der Bilt.

They collected a sediment core from the lake containing 7,000 years of climate history, and during laboratory analyses they discovered something surprising. 

“We found out that these little layers we saw already during fieldwork were minerals that form in the lake under very specific conditions, when there is no oxygen in the water. The longer the lake is covered by ice, the less oxygen is found in the water, which is directly linked to winter climate,” van der Bilt explains.

A combination of methods

In the study, the researchers combined established laboratory methods with new scanning techniques.

Medical CT scans were used to find minerals that were often invisible. The contents were then examined more closely using microscopic analyses.

The researchers also used hyperspectral imaging, a method that can recognise different materials based on their light spectra. Here, they used the method to find pigments from bacteria that lived in the lake when oxygen levels were low.  

They found that variations in winter climate follow a well-known 1,500-year climate cycle.

“You can think of it as the heartbeat of natural climate in this area. But we are the first to report that it also has an impact on winter climate on land,” van der Bilt says. 

“So, depending on where you are in that cycle in a future also shaped by human climate warming, that cycle could either make the impacts of human climate change worse or dampen it a little bit,” he adds.

Volcanic eruptions can lead to cold winters

The next important finding is that almost every extreme winter they found in the lake appears to have occurred shortly after several volcanic eruptions happening within a short period.

Volcanic eruptions inject large clouds of particles and gases into the atmosphere, which can block incoming sunlight for years to decades.

You can read more about the phenomenon in this article on Science Norway.

“By combining all kinds of fancy scanning and microscope techniques, we find that these extreme volcanic winters happened throughout the past 8,000 years, regardless of the background state of climate, meaning they happened under warm and cold conditions. That means that extremely cold volcanic winters may also happen in the warmer future that the region faces,” says van der Bilt.

Reference:

van der Bilt et al. Siderite Concretions in Svalbard Lake Sediments Capture 7,000 Years of Extreme Arctic Cold Season Climate Change, Geophysical Research Letters, 2026. DOI: 10.1029/2026GL122061

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