Why the Norsemen had to give up Greenland
For centuries, Northmen settled in Greenland despite harsh conditions. At the end of the Middle Ages, they had to give up, but it was probably not the cold that was to blame.
It is an unsolved mystery why the south of Greenland was first successfully settled by Norsemen in the early Middle Ages, but then abandoned rather suddenly after a few centuries. There are several theories about the reasons for the abandonment of the settlements in the early 15th century: It is possible that the global cooling during the Little Ice Age made life on Greenland insidiously unbearable. This may have been compounded by an unsustainable use of resources due to growing global competition. A new analysis now brings the climate back into focus as the main cause - however, it was probably not too cold for settlement on Greenland in the long term, but above all far too dry.
To this conclusion comes a research team around Raymond Bradley of the Amherst University in the technical periodical "Science Advances". The researchers were the first team to collect data on site in the old settlement area in order to reconstruct the microclimate there in the Middle Ages. Earlier studies had conducted historical climate reconstructions using ice cores retrieved from Greenland ice nearly 1,000 kilometers to the north at higher altitudes. However, conditions in southern Greenland were different even in the 15th century, the new research shows.
Bradley's team took samples over three years from "Lake 578," a lake located in close proximity to one of the largest abandoned Norse settlements in southeastern Greenland. From the ice cores, it reconstructed weather changes over two millennia. Temperature changes are revealed to researchers by so-called GDGTs, certain branched lipid molecules produced by bacteria and archaea and contained in the ice of the cores, which is frozen year after year. The branching structure of these molecules depends on the ambient temperature in which the bacteria lived. In addition, the researchers were able to determine the change in humidity over time, using as a marker a certain waxy molecule that plants deposit in greater or lesser quantities on their leaf surfaces to protect themselves more or less from desiccation.
As the analysis shows, it was not unbearably cold in southern Greenland during the Little Ice Age. It is true that the ice tongues of the glaciers grew locally: According to calculations by the working group, the Kangiata Nunaata Sermia, for example, gained up to 115 meters of ice year after year and rapidly approached the settlements of the Greenlanders. However, this should not have disturbed them very much. Presumably, the rapidly growing glacier tongue even calved fewer icebergs into the sea, which may have facilitated access to the sea for the local people.
What was striking, however, was that while the average temperature over the entire settlement period of the Norsemen from 985 AD to the 15th century was almost the same as in the previous century, the average temperature in the same period was almost the same as in the previous century. Z. until the 15th century remained almost the same, the dryness increased more and more. This must have had severe consequences, especially in winter: The Norsemen were dependent on keeping their livestock alive with stored fodder until spring. The authors of the study speculate that it was probably simply not possible to grow enough crops under the dry conditions. The settlers were obviously aware of the problem: At the end of the settlement phase, they had begun to dig irrigation grooves for fields - an ultimately insufficient countermeasure. In addition, they increasingly had to resort to other food sources such as fish and seafood.
At the height of Greenland settlement, up to 2000 people had lived in the eastern settlements. There were other settlements in the west of the island. These were abandoned even earlier: A Norwegian priest had encountered no living "Grænlendingar" there as early as 1350.
Spectrum of Science
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