Scientists may have found an important factor behind why the Norse mysteriously abandoned their largest settlement on Greenland. And it wasn't cold weather, as some had long thought.
Rather, drought might have played a major role in the abandonment of the Eastern Settlement of Vikings around 1450, new research suggests.
"We conclude that increasingly dry conditions played a more important role in undermining the viability of the Eastern Settlement than minor temperature changes," a team of scientists – many of whom are based at the University of Massachusetts Amherst – wrote in an article published online March 23 in the journal Science Advances.
"Drier climate would have notably reduced grass production, which was essential for livestock overwintering, and this drying trend is concurrent with a Norse diet shift" toward seafood, the team wrote.
The Vikings first settled in Greenland in A.D. 985, establishing the Eastern Settlement along the southwestern fjords, and a smaller settlement, known as the Western Settlement, 240 miles (385 kilometers) to the northwest. The Eastern Settlement eventually grew to hold around 2,000 people at its peak. The Western Settlement was abandoned during the 14th century while the Eastern Settlement held out until around 1450.
The researchers spent three years collecting sediment samples from a lake near the Eastern Settlement, to gather data on what the climate was like close to where the Norse lived. .
Past climate reconstructions in Greenland have often relied on ice cores taken from locations far away from where the Norse settlement existed, the researchers said in a statement. These earlier reconstructions indicated that the region experienced a significant temperature drop around the year 1300. However, the team wanted climate data gathered closer to an actual settlement.
"We wanted to study how climate had varied close to the Norse farms themselves," Raymond Bradley, a geosciences professor at University of Massachusetts Amherst and study co-author, said in the statement.
An analysis of the sediment cores showed that a dry period started around 950, before the Norse even arrived, and the situation gradually got worse before stabilizing during the 16th century.
The team measured organic carbon and pigments called chlorins in the sediment cores to determine how wet it was. Lower levels indicate that the climate was drier as there was less water to carry organic carbons and chlorins into the lake. To measure temperature, the team analyzed the amount of a lipid called BrGDGT in the sediment cores.
There was no indication in the sediment analysis that temperatures dropped significantly in the area during the time that the Eastern Settlement existed. On the other hand, previous research has shown that the Western Settlement did experience a significant temperature drop, study co-author Boyang Zhao, a postdoctoral research associate at Brown University's department of Earth, Environmental, and Planetary Sciences, told Live Science. Previous research also suggested that rising sea levels played a role in the demise of the Eastern Settlement. The team’s research did not examine whether this flooding took place.
The findings suggest that drought played a role in the Eastern Settlement’s demise, although the team said that this was not the only cause of the decline. "As we noted in our paper, drought is never the sole reason that the Norse [vanished]" Zhao told Live Science in an email.
Live Science talked to a number of scholars not affiliated with the research to get their thoughts on the finds. Scholars were generally supportive of the finding that the Norse in Greenland experienced a drought; however, some questioned the finding that the temperature didn't drop significantly in the Eastern Settlement, and some scholars also raised questions about how big of an impact the drought had on the Norse.
The findings could explain previously discovered evidence that the Norse were building irrigation systems in Greenland. "The conclusions appear to further highlight the real need that Norse farmers would have had to irrigate their hay fields to buffer against periods of drought," Edward Schofield, a senior lecturer in geosciences at the University of Aberdeen in Scotland, told Live Science in an email.
A drought also fits well with some climate findings. This drought was "most likely part of a major change in the complex ocean-atmosphere interaction regime in which a windy, more moist climate in southern Greenland was gradually being replaced by [a drier climate]," Antoon Kuijpers, a geologist with the Geological Survey of Denmark and Greenland, told Live Science in an email.
The team's findings that the Eastern Settlement did not experience a large temperature drop was surprising. "Given that quite a few other types of proxy data from Greenland do suggest cooling across this same time period, that's something that I suspect will make people wonder," Kevin Smith, a senior research fellow at the Haffenreffer Museum of Anthropology at Brown University, told Live Science in an email.
Additionally, some scholars didn't think the level of drought discovered could have played a crucial role in the demise of the Norse Greenland colony. The research "does not demonstrate that the drying was on a scale which would have resulted in a significant reduction in utilisable biomass, so it remains to be shown to what extent the proposed drying trend could have been an actual problem for farming," Orri Vésteinsson, an archaeology professor at the University of Iceland, told Live Science in an email.
"There is no evidence that the Norse Greenlanders were facing any kind of subsistence crisis, so even if poorer hay harvests and less productive pastures might have contributed to the increased reliance on marine foods, it would not work as an explanation for the demise of the settlements — they still had plenty of food in the pantry," Vésteinsson said.
Other scholars noted that even if the drought played a significant role in the demise of the Norse settlements in Greenland, there were likely many other factors that were also important. For instance, Smith noted that historical records say that between 1402 and 1404, an epidemic (likely the bubonic plague) ravaged Iceland, killing as much as half the population. With many farms in Iceland laying abandoned, the Norse in Greenland may have been tempted to move to Iceland, Smith said, noting that conditions in Iceland were "far better for the kind of farming they [the Norse] knew how to do."
Originally published on Live Science.