Vikings Were Fearless. Except When It Was Too Cold

Greenland was balmy when the Vikings invaded, a new study based on isotopes in flies has proven, and they left as the glaciers bore down

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Aerial view of the Greenland ice sheet from a helicopter.
Aerial view of the Greenland ice sheet from a helicopter.Credit: G. Everett Lasher / Northwestern
Ruth Schuster
Ruth Schuster
Ruth Schuster
Ruth Schuster

Vikings evoke many associations, none of which involve relaxing on the seaside and smelling flowers on a balmy evening. The Scandinavian warriors are more usually perceived as being roughnecks in horned helmets who laughed off subzero temperatures. And maybe they did, but a new study by Northwestern University, published this week in Geology, has proven the theory that when the Vikings braved the violent northern seas and conquered Greenland from auks in the 10th century, the island’s climate was less merciless and more Mediterranean.

Aerial view of farm in southern Greenland, seen from a helicopter.
Aerial view of farm in southern Greenland, seen from a helicopter.Credit: G. Everett Lasher / Northwestern

Also, the Vikings suddenly disappeared from Greenland in the middle of the 15th century, just as the warm snap was ending and the glaciers were sweeping down. A combination of factors seems to have crushed the formerly prosperous settlement, but cold seems to have been key. They could either go native and become horn-helmeted Inuits, or leave. They left.

Greenland has a history of sporadic settlement by various peoples who ultimately despaired of the forest-free island and moved on. The earliest known paleo-Eskimo settlers arrived in the island at least 4,500 years ago, and hung on for thousands of years. They would be followed much later by the Inuits, originating in Alaska.

A 21st-century reproduction of Erik the Red’s house on his estate (known as Brattahlíð) in present day Qassiarsuk, Greenland.
A 21st-century reproduction of Erik the Red’s house on his estate (known as Brattahlíð) in present day Qassiarsuk, Greenland. Credit: G. Everett Lasher / Northwestern

Vikings, led by Erik the Red (named either for his fiery locks or murderous ways), were known to have reached Greenland in the year 985 or 986. In fact, according to history, Erik is the one who gave the island that name in order to attract more settlers. But maybe he did not tell a lie.

Aerial view of the village of Igaliku, Greenland, former site of the Norse settlement Garðar.
Aerial view of the village of Igaliku, Greenland, former site of the Norse settlement Garðar. Credit: G. Everett Lasher / Northwestern

“People have speculated that the Norse settled in Greenland during an unusually, fortuitously warm period, but there weren’t any detailed local temperature reconstructions that fully confirmed that. And some recent work suggested that the opposite was true,” said Northwestern’s Yarrow Axford, the study’s senior author. “This has been a bit of a climate mystery.”

Mud builds up at the bottom of lakes, so as long as they remain undisturbed (e.g., by earthquake), cores taken from lake sediment are like a record of the past. In Israel, for instance, sediment cores from the Dead Sea have proven not just local aridity but protracted “megadrought.”

Dew-drop-coated flowers grow in the foreground against the backdrop of the iceberg-filled ocean in southern Greenland.Photo credit: G. Everett Lasher/Northwestern University
Dew-drop-coated flowers grow in the foreground against the backdrop of the iceberg-filled ocean in southern Greenland.Credit: G. Everett Lasher / Northwestern

So, to resolve the mystery once and for all, the team reconstructed Greenland’s climate history over the last 3,000 years using lake sediment cores ­– which contained a lot of dead flies.

As the Viking flies

The team analyzed oxygen isotopes in the exoskeletons of these chironomid flies, who had died and descended to the bottom of the lake over the centuries. Chironomids are a vast family of insects that look like mosquitoes but aren’t mosquitoes. Anyway, while Greenland’s climatic fluctuations has discouraged the entrenchment of both major plant and animal life over the eons, the flies thrive.

Collected and cleaned chironomid head capsules are prepped for isotope analysis.
Collected and cleaned chironomid head capsules are prepped for isotope analysis.Credit: G. Everett Lasher / Northwestern

Thus, the team concluded that when the Vikings were in Greenland from 985 to 1450, the weather was warm compared to the previous and following centuries.

Overall, they write, the climate was about 1.5 degrees Celsius warmer than in the preceding and following centuries. In summer, the ambient temperature could reach a balmy 50 degrees Fahrenheit (a whopping 10 degrees Celsius). Tel Aviv it isn’t, but howling blizzard it isn’t either.

The oxygen isotopes in the chironomids record the lake water isotopes when the flies were alive, explain G. Everett Lasher and Axford. In turn, the lake water isotopes are a function of the oxygen isotopes in the rain, which has to do with temperature. The bottom line is that the change in oxygen isotopes in the bugs over time infers how temperature might have changed.

An up-close look at a chironomid’s head capsule(center) under a microscope.The Northwestern team isolates these exoskeletons from sediment cores collected in southern Greenland for oxygen isotope analysis.
An up-close look at a chironomid’s head capsule(center) under a microscope.The Northwestern team isolates these exoskeletons from sediment cores collected in southern Greenland.Credit: G. Everett Lasher / Northwestern

So they concluded that when the Vikings were there, the weather was pretty terrific by Greenlandic standards.

Northwestern University Ph.D. candidate Everett Lasher rests in his tent in the team’s camp in southern Greenland, summer 2016.
Northwestern University Ph.D. candidate Everett Lasher rests in his tent in the team’s camp in southern Greenland, summer 2016.Credit: Jamie McFarlin / Northwestern Un

Based on the archaeological finds of their stone homes and other things, it seems the Viking settlement had been quite successful – peaking at about 5,000 people, who were a mix of pagans and Christians. But Greenland has no forests, and they had been dependent on trade with their home nations in Scandinavia for staples like wood and iron, in exchange for which they would sell walrus and narwhal tusks, and the like.

But it was not to last. Little did the Vikings know it but their farming practices were ecologically unsound, to put it politely, and the Scandinavian appetite for polar bears and walrus teeth would wane. Trade with Norway, never robust, stopped completely.

Also, those 500 years of warm weather were a mere climatic hiatus. Glaciers were advancing around Greenland and in the Canadian Arctic throughout their sojourn. The warm period merely interrupted the consistent cooling climate trend, driven by changes in Earth’s orbit.

Previous archaeological studies indicate that as the weather got colder and colder, the Greenland Vikings did not cavil at living with their domestic animals, for the warmth. “Near the end of the warm period, the climate was exceptionally erratic and unstable with record high and low temperatures,” the team writes.

Nobody knows what happened to the last descendants of the Vikings in Greenland. Some theorize that they stubbornly clung to their Scandinavian ways, scornfully failed to emulate the Inuit methods of survival in the icy north, and were thus doomed. They may have been killed – not necessarily by irked Inuits but possibly by pirates (who were known to plague Iceland).

Or maybe they sailed back to Scandinavia, or possibly even headed for the New World. The only problem with that theory is that by the time the Vikings abandoned Greenland, the remaining community was clearly in bad shape, cold, and starving. Absent a source of wood planks and iron nails to fix their aging boats, one may doubt whether they could get far.

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