May 31, 2011

Little Ice Age Drove Vikings From Greenland

The end of the Norse colonies on Greenland have long been shrouded in mystery, and while archaeologists have been able to fill in some blanks, there is limited written evidence of the colony's demise in the 14th and early 15th century.

But now, new research from Brown University suggests that Greenland's early Viking settlers lived in a region with a rapidly changing climate with temperatures plunging several degrees on average in a span of decades.

Climate scientists have been able to ascertain that an extended cold snap, known as the Little Ice Age, took hold in Greenland beginning in the 1400s, which has been cited as a major cause of the Norse's disappearance from the region.

Scientists reconstructed 5,600 years of climate history from two lakes in Kangerlussuaq near the Norse settlement in western Greenland.

Unlike the ice cores taken from the Greenland ice sheet hundreds of miles inland, the new lake core samples reflect air temperatures where the Vikings lived, as well as those experienced by the Saqqaq and Dorset, Stone Age cultures that preceded them.

"This is the first quantitative temperature record from the area they were living in," said William D'Andrea, lead author of the paper on the study, who earned his doctorate in geological sciences at Brown and is now a postdoctoral researcher at the University of Massachusetts"“Amherst. "So we can say there is a definite cooling trend in the region right before the Norse disappear."

"The record shows how quickly temperature changed in the region and by how much," said Yongsong Huang, professor of geological sciences at Brown, principal investigator of the NSF-funded project, study co-author and D'Andrea's Ph.D. adviser. "It is interesting to consider how rapid climate change may have impacted past societies, particularly in light of the rapid changes taking place today."

While climate may have been the main driver of the Vikings' demise in the western settlement, it is not the only factor. The Vikings' sedentary lifestyle, reliance on agriculture and livestock for food, dependence on trade, and their combative relations with nearby Inuit, are also believed to be contributing factors.

The Vikings arrived in Greenland just before 1000 AD, establishing a line of small communities along Greenland's western coast. Their arrival coincided with a time of relatively mild weather, similar to that of Greenland today. However, beginning around 1100, the climate began an 80-year average downturn of 7 degrees Fahrenheit, Brown scientists concluded.

While that figure may not sound to overwhelming, especially during summer months, the change could have led to a number of issues, including shorter growing seasons for crops, less available food for livestock and more sea ice that may have blocked trade routes.

"You have an interval when the summers are long and balmy and you build up the size of your farm, and then suddenly year after year, you go into this cooling trend, and the summers are getting shorter and colder and you can't make as much hay. You can imagine how that particular lifestyle may not be able to make it," said D'Andrea.

Recovered records show that the Western Settlement vanished sometime in the mid-1300s, and another settlement, known as the Eastern Settlement, which was located further south, existed until the early 1400s.

The researchers also studies how the climate affected the Dorset and Saqqaq people. The Saqqaq arrived in Greenland in 2500 BC. While there were warm and cold snaps for centuries after their arrival, the climate took a longer cold drop beginning roughly around 850 BC, the researchers discovered.

"There is a major climate shift at this time," said D'Andrea. "It seems that it's not as much the speed of the cooling as the amplitude of the cooling. It gets much colder."

The Saqqaq's exit coincides with the arrival of the Dorset, who were more accustomed to hunting from the sea ice that would have existed in the colder climate at that time. Yet by about 50 BC, the Dorset culture was dwindling in western Greenland, despite its ability to thrive in the colder climate.

"It is possible that it got so cold they left, but there has to be more to it than that," said D'Andrea.

Contributing authors include Sherilyn Fritz from the University of Nebraska"“Lincoln and N. John Anderson from Loughborough University in the United Kingdom. The National Science Foundation funded the work.

Results of the study appear in the journal Proceedings of the National Academy of Sciences.


Image 2: William D'Andrea, right, and Yongsong Huang took cores from two lakes in Greenland to reconstruct 5,600 years of climate history near the Norse Western Settlement. Credit: William D'Andrea/Brown University


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