Surviving climate change in 6th century Finland

Norse myths tell of a time called “fimbulwinter” – when the world will be struck by three consecutive winters, with constant snows and no summer. This might actually have happened in the mid-sixth century, and a newly published article is showing how people in Finland survived the disaster.

A multidisciplinary research group coordinated by the University of Helsinki has been investigated an archaeological site in Finland, and looking at how people there reacted to a severe climate disaster in the 540s. It was during this period that volcanic eruptions initiated a cold and dark period lasting several years, possibly reflected in folktales across the northern hemisphere. Recently the researchers have found a link between the disaster and a reduction in the quantity of light observed in the carbon isotopes found in the annual growth rings of trees in Lapland between 541 and 544.


“If you want to date Fimbulwinter, the three successive winters mentioned in Scandinavian sagas, this is the best candidate,” explains Docent Markku Oinonen, director of the Laboratory of Chronology at the University of Helsinki.

Oinonen is heading a research team, which is studying the bones of dozens of early medieval residents of the Levänluhta site in Finland, examining their carbon and nitrogen stable isotope ratios. The results provide an overview of the dietary habits based on terrestrial, marine and freshwater ecosystems, as well as of sources of livelihoods throughout the Levänluhta era.


Remains from Levänluhta at the National Museum of Finland – photo by Daderot / Wikimedia Commons

Ever since the 17th century, human bones have been emerging from the spring-containing lake burial site at Levänluhta in Southern Ostrobothnia, western Finland. These remains, which date between the 4th and 9th centuries, reveal a diverse community that relied on an extremely broad range of livelihoods, which matches well with the understanding provided by archaeological discoveries.

“The isotope data of the human remains at Levänluhta is divided into three clearly distinct groups, a unique occurrence around the Baltic Sea area,” explains Oinonen.

Fimbulwinter has been said to have caused a collapse in farming in the areas surrounding Sweden and Estonia. However, the ratio of food from terrestrial sources consumed by the Levänluhta population does not decrease after this period. Instead, the group relying heavily on marine food starts to fade out. The largest group of people continued to supplement their diet with marine food, actually increasing its presence in the human remains buried in the middle of the 7th century. Protein-rich food indicates produce derived from animals, and it appears that, instead of farming, most of the population probably based their sustenance on animal husbandry and hunting. In fact, fur trade has traditionally been thought as the source of wealth during the Iron Age in these southern roots of the Suomenselkä water divide.

Prior genetic research and place name data indicate a connection between the Levänluhta population and the Sámi. Signs of the diverse livelihoods of Iron Age Sámi have also been previously observed in Sweden on the same latitudes. Indeed, the researchers are considering whether the lake burial site of Levänluhta could be a manifestation of sáivas, the sacred spring-containing lakes in the Sámi mythology.


The amount of radiocarbon, the radioactive isotope of carbon, serves as evidence of time periods, while the ratios of stable isotopes relate to the food sources used. By combining methods, researchers can build time series on changes in human diets and livelihoods over time.

Researchers at the University of Helsinki have carried out almost 40 radiocarbon and carbon and nitrogen isotope analyses with the bone material excavated from Levänluhta. Combining these findings with an extensive background dataset on the isotope values of nutrients and their relative quantities has enabled the conduct of dietary modelling and time series analyses throughout the Levänluhta period.

The article “Buried in water, burdened by nature—Resilience carried the Iron Age people through Fimbulvinter” has been published in Plos One. Click here to read it.


Top Image: Levänluhta is among the most unique archaeological sites, even on a global scale. Bones belonging to nearly a hundred individuals who died in the Iron Age have been discovered in the middle of the Southern Ostrobothnia plains in western Finland since the 17th century. Today, three springs and their ferrous red water serve as reminders of this ancient burial site. Photo by Anna Wessman / University of Helsinki