A new study questions the popular notion that 10th-century Norse people were able to colonize Greenland because of a period of unusually warm weather. Based upon signs left by old glaciers, researchers say the climate was already cold when the Norse arrived--and that climate thus probably played little role in their mysterious demise some 400 years later. On a larger scale, 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.
"It's becoming clearer that the Medieval Warm Period was patchy, not global," said lead author Nicolás Young, a glacial geologist at Columbia University's Lamont-Doherty Earth Observatory. "The concept is Eurocentric--that's where the best-known observations were made. Elsewhere, the climate might not have been the same." Climate scientists have cited the Medieval Warm Period to explain anomalies in rainfall and temperature in far-flung regions, from the U.S. Southwest to China. The study appears today in the journal Science Advances.
Norse, or Vikings, led by Erik the Red, first sailed from recently settled Iceland to southwestern Greenland around 985, according to Icelandic records. Some 3,000 to 5,000 settlers eventually lived in Greenland, harvesting walrus ivory and raising livestock. 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 (also known as the Medieval Climate Anomaly), generally dated from about 950-1250; their disappearance followed the onset of the Little Ice Age, which ran from about 1300-1850. Both periods are firmly documented in European and Icelandic historical records. Thus, popular authors and some scientists have fixed on the idea that nice weather drew the settlers to Greenland, and bad weather froze and starved them. But there are no early historical climate records from Greenland. Recently, historians have proposed more complex factors in addition to, or instead of, climate: hostilities with the Inuit, a decline in ivory trade, soil erosion caused by the Vikings' imported cattle, or a migration back to Europe to farms depopulated by the Black Plague.
In the new study, the scientists sampled boulders left by advancing glaciers over the last 1,000-some years in southwest Greenland, and on neighboring Baffin Island, which the Norse may also have occupied, according to newly uncovered evidence. Glacial advances during the Little Ice Age have wiped out most evidence of where the glaciers were during the Norse settlement. But Young and his colleagues were able to find 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 analyzing 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. The strong implication: it was at least as cold when the Vikings arrived as when they left. "If the Vikings traveled to Greenland when it was cool, it's a stretch to say deteriorating climate drove them out," said Young.