Contrary to the popular belief, Vikings did not colonise Greenland because of a period of unusually warm weather, according to a new study.
Based upon signs left by old glaciers, researchers found that the climate was already cold when the 10th-century Norse people arrived - and that climate thus probably played little role in their mysterious demise some 400 years later.
The study adds to building evidence that the so-called Medieval Warm Period, when Europe enjoyed exceptionally clement weather, did not necessarily extend to other parts of the world, researchers said.
"We were surprised by our findings that glaciers in Greenland were healthy and large when the Norse were there, and also when Europe was experiencing warmth," said study co-author Jason Briner, an associate professor of geology in the University at Buffalo College of Arts and Sciences.
"It's becoming clearer that the Medieval Warm Period was patchy, not global," said lead author Nicolas Young, a glacial geologist at Columbia University.
Norse, or Vikings, led by Erik the Red, first sailed from recently settled Iceland to southwestern Greenland around 985, according to Icelandic records.
But the colonies disappeared between about 1360 and 1460, leaving only ruins, and a longstanding mystery as to what happened. The native Inuit remained, but Europeans did not re-inhabit Greenland until the 1700s.
The Greenlandic Vikings' apogee coincided with the Medieval Warm Period generally dated from about 950-1250; their disappearance followed the onset of the Little Ice Age, which ran from about 1300-1850.
Climate scientists have cited the Medieval Warm Period to explain anomalies in rainfall and temperature in far-flung regions.
In the new study, the scientists sampled boulders left by advancing glaciers over the last 1,000-some years in southwest Greenland, and on neighbouring Baffin Island, which the Norse may also have occupied.
They found traces of a few moraines - heaps of debris left at glaciers' ends - that, by their layout, they could tell predated the Little Ice Age advances.
Using newly precise methods of analysing chemical isotopes in the rocks, they showed that these moraines had been deposited during the Viking occupation, and that the glaciers had neared or reached their later maximum Little Ice Age positions between 975 and 1275.
"If the Vikings travelled to Greenland when it was cool, it's a stretch to say deteriorating climate drove them out," said Nicolas Young, a geologist at Columbia University.
The findings were published in the journal Science Advances.
