Science Gazette

Rewriting History: Why Did the Vikings Leave Greenland?

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Why did the Norse, who had created prosperous colonies in southern Greenland in 985, forsake them in the early 15th century is one of the great riddles of late medieval history. Colder temperatures linked with the Little Ice Age, according to popular belief, contributed to the colonies’ demise. However, new study done by the University of Massachusetts Amherst and just published in Science Advances calls that old idea into question. The Norse were driven from Greenland by drought, not cold weather.

When the Norse arrived in Greenland in 985 and established the Eastern Settlement, they flourished by clearing the area of bushes and planted grass as grazing for their animals. The Eastern Settlement’s population peaked at roughly 2,000 people, but it declined rapidly around 400 years later. For decades, anthropologists, historians, and biologists believed the Eastern Settlement’s death was caused by the start of the Little Ice Age, a time of unusually cold weather, notably in the North Atlantic, that rendered agricultural life in Greenland unviable.

However, as Raymond Bradley, University Distinguished Professor of Geosciences at UMass Amherst and a co-author of the report, points out, “There was no data from the actual location of the Viking settlements prior to our study. That is an issue.” Instead, earlier research employed ice core data from a site nearly 1,000 kilometers north and over 2,000 meters higher in elevation to recreate past temperatures in Greenland. “We wanted to look at how climate changed around the Norse farms,” Bradley explains. And when they did, the findings were unexpected.

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Bradley and his colleagues went to Lake 578, which is near a former Norse farm and one of the biggest clusters of farms in the Eastern Settlement. They spent three years there collecting silt samples from the lake, which offered a continuous record for the last 2,000 years. “Nobody has ever examined this site before,” says Boyang Zhao, the study’s primary author, who earned his Ph.D. in geosciences at UMass Amherst and is now a postdoctoral research associate at Brown University.

The 2,000-year sample was then tested for two separate markers: the first, a lipid known as BrGDGT, may be used to reconstruct temperature. “If you have a thorough enough record, you can directly correlate changing lipid structures to changing temperature,” says Isla Castaeda, a geosciences professor at UMass Amherst and one of the paper’s co-authors. A second marker obtained from the waxy coating on plant leaves may be used to calculate the rates at which grasses and other livestock-sustaining plants lost water via evaporation. As a result, it is an indication of how dry the circumstances were.

“What we observed is that, although the temperature scarcely changed throughout the Norse occupation of southern Greenland,” Zhao explains, “it grew gradually dryer over time.”

Norse farmers had to feed their cattle stockpiled hay during the winter, and even in a good year, the animals were often so feeble that they had to be carried to the fields once the snow melted in the spring. Drought would have had disastrous implications under such situations. A prolonged drought, along with other economic and social stresses, may have shifted the scales just enough to render the Eastern Settlement untenable.

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The study, which was funded by the National Science Foundation, UMass Amherst, the Geological Society of America, and the Swiss National Science Foundation, changes our understanding of early European history and emphasizes the importance of continuing to investigate how environmental factors influence human society.

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