One of the great mysteries of late medieval history is why the Norse (people who inhabited the now Scandinavian countries including Sweden, Denmark, Norway, and Iceland) had abandoned southern Greenland where they established successful settlements.
The consensus view has long been that colder temperatures, associated with the Little Ice Age, helped make the colonies unsustainable. However, new research, led by the University of Massachusetts Amherst and published recently in the journal Science Advances, upends that old theory, suggesting that what helped drive the Norse from Greenland was drought.
When the Norse settled in Greenland on what they called the Eastern Settlement in 985, they thrived by clearing the land of shrubs and planting grass as pasture for their livestock. The population of the Eastern Settlement peaked at around 2,000 inhabitants but collapsed quickly about 400 years later.
For decades, anthropologists, historians and scientists have thought the Eastern Settlement's demise was due to the onset of the Little Ice Age, a period of exceptionally cold weather, particularly in the North Atlantic, that made agricultural life in Greenland untenable.
However, as Raymond Bradley, professor of geosciences at UMass Amherst and one of the paper's co- authors points out, "before this study, there was no data from the actual site of the Viking settlements. And that's a problem. Instead, the ice core data that previous studies had used to reconstruct historical temperatures in Greenland was taken from a location that was over 1,000 kilometers to the north and over 2,000 meters higher in elevation.”
"We wanted to study how climate had varied close to the Norse farms themselves," said Bradley. And when they did, the results were surprising. Bradley and his colleagues traveled to a lake called Lake 578, which is adjacent to a former Norse farm and close to one of the largest groups of farms in the Eastern Settlement. There, they spent three years gathering sediment samples from the lake. They collected 2,000 samples.
They then analyzed sample for two different markers: the first, a lipid, known as BrGDGT, can be used to reconstruct temperature, and to directly link the changing structures of the lipids to changing temperature. A second marker, derived from the waxy coating on plant leaves, can be used to determine the rates at which the grasses and other livestock-sustaining plants lost water due to evaporation. It is therefore an indicator of how dry conditions were.