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Just a couple of kilometers inland from the coast of Northern Iceland, lie Torfdalsvatn, a small, deep freshwater lake. Winters here are frigid, snowy and dark, save a few hours of muted daylight. Lucky visitors might catch a glimpse of the Northern Lights when the clouds clear.

Most travelers opt to visit the region in the summer, when conditions are more temperate, but for paleoclimate researchers, winter is the perfect time for a trip to Torfdalsvatn. That’s because the mud that lies below the lake holds an exceptionally detailed record of Earth’s past. And, in the winter, researchers can bring the cumbersome equipment needed to drill down into the mud right out on the ice with them.

“You can drive right out onto the ice and drill through with an ice auger,” CIRES research scientist and INSTAAR affiliate David Harning explained. “It’s much harder in the summer when you’re out in a little boat trying to anchor it and it’s windy and our boat is getting dumped on.”

Last month, Harning, along with American and Icelandic collaborators, published�� built on decades of research at Torfdalsvatn. The study brings diverse analytical methods together to provide a highly detailed picture of past climatic conditions, soil stability and plant life at the site.��

One clear takeaway was that Torfdalsvatn’s soils and plant communities remained exceptionally resilient, when compared to other sites in Iceland. It’s an insight that is more than a piece of history—it could help conservationists better plan for the future.

“Soil erosion is one of the biggest problems in Iceland right now,” Harning said. “Understanding the resilience or fragility of certain areas to future changes in soil erosion is really important to conserving these landscapes.”

Fire and ice in the mud

, researchers have looked to the sediments below Torfadalsvatn to understand the past 12,000 years of climatic conditions in Iceland. The site is an exceptionally good model of the past for two reasons.��

Firstly, sediment piles up at the bottom of Torfadalsvatn at an unusually high clip, leaving researchers more mud to analyze. Secondly, Torfadalsvatn was one of the first lakes to emerge, when the giant ice sheet that once stretched across Iceland began to retreat 12,000 years ago. As a result, the lakebed houses some of the oldest sediment in the country.

Over the past three decades, much of the work on Torfadalsvatn’s sediment record has been done by two researchers and their students:��INSTAAR faculty fellow Gifford Miller and University of Iceland professor of geology Áslaug Geirsdóttir.

Harning, a former student of both, was brought in on the project during his PhD studies at INSTAAR. Between other projects, he worked to identify layers of volcanic ash in the sediment (Iceland is known as “the land of fire and ice” because of its plentiful active volcanoes).��

Over the lifetime of the project, several other researchers devoted countless hours to other analyses. These included identifying algal pigments and geochemical markers, proxies for past plant communities and climate respectively.

In the new study, Harning pairs these previous analyses with a suite of techniques meant to place each data point more precisely in time.��

Áslaug Geirsdóttir prepares the sediment coring device at Torfdalsvatn. Due to the lake’s high sedimentation rates, this 3 meter long tube will only recover around 3,000 years of mud. Multiple subsequent cores are then required to collect the entire 12,000 year history. Photo courtesy of David Harning.

“By establishing the chronology and locking sedimentary history in time, we could start to ask some of these longstanding questions that our group has been interested in,” he said.

One of these questions, perhaps the most controversial one, concerns soil erosion and human settlement. There is a longstanding theory that��.��, suggesting that these changes could have been kicked off by environmental changes even further in the past.

Harning’s analysis, though, complicates the theory even further. The researchers estimated that erosion and vegetation changes at Torfadalsvatn didn’t escalate until around 200 years after the arrival of settlers. Perhaps something about the site made it more resistant to whatever factors caused degradation elsewhere.

“We weren’t expecting that,” Harning said. “This implied that the site, which is coastal and at a low elevation, had some sort of natural resilience to the processes that were causing soil erosion elsewhere.”

Looking Forward

Harning urges that further research should look into what made Torfadalsvatn so resilient. The question is still relevant today,��.

Harning and his colleagues’ recent paper could also provide useful information for other scientific fields. The analysis provides an exceptionally detailed record of past volcanic events, many of which had not been previously identified. If corroborated, these markers could provide, essentially, a time stamp in the sediment record to aid future research.

“It’s a ton of information about volcanic history,” Harning said. “Maybe someone else finds another link, and then you have new marker layers.”

Finally, the new analysis provides a huge amount of information relating past climatic conditions to ecological conditions. This information isn’t only useful for researchers curious about ancient history, it could also help scientists look to the future.

“These high resolution records are a key data constraint for any Earth system model that’s trying to predict future climate change,” Harning said. “If you have a good understanding of the physics of the system, you can run that model forward.”