How cascading crises may have chased Viking settlers from North America

Rising seas and increased flooding may have helped chase Viking colonists out of Greenland, a new study has found.

The study offers a new explanation to a medieval mystery: why Viking settlements on the doorstep of North America failed on the eve of European contact with the continent’s peoples.

In the new account, rising seas — pulled toward lowland settlements and harbors by the greater gravitational pull of growing ice sheets — pushed the colony “to a tipping point,”

lead author Marisa Borreggine of Harvard University told The Hill.

The study in Proceedings of the National Academy of Science adds additional color to a stark — and strikingly modern — story of a society struggling for generations to adapt in the face of complex environmental change.

In the case of Greenland, as along today’s coastlines, that threat was the dual risk of devastating floods and the slow, implacable infiltration of crop-destroying saltwater, Borreggine found.

But unlike today, the cause of that sea level rise was global cooling, not planetary heating. 

As the Little Ice Age dropped global temperatures and greater volumes of North Atlantic waters frozen into the great Greenland ice cap, “intuition might suggest that sea level should go down,” Borreggine said. 

But that intuition fails in the face of the sheer size of the Greenland ice cap — which is so large that its gravity pulled the waters of the North Atlantic inward, causing localized sea level rise.

At the same time, the added weight of ice pushed down the Earth’s crust, causing Norse colonies to experience “a double whammy” of falling earth and invading oceans, Borreggine said.

That combination led to the ocean coming inland at “two to six times the rate of 20th-century sea-level rise,” the authors found. 

Put another way, the sea-level rise was equivalent to that projected for later this century under some of the worst scenarios for climate change — ones in which global combustion of fossil fuels doesn’t halt.

Over the 400-year life of the colony, that translated to 3.3 meters, or about 10 feet, of sea level rise, the study found.

The combination of new modeling techniques and the discovery of ancient, drowned Norse buildings suggested a “pervasive” flooding problem, the researchers found.

Three-quarters of Viking settlements were within about half a mile of sites of severe flooding.

Like modern society, environmental stressors contributed to a broader set of challenges facing Norse settlers.

“Environmental change does not exist in a vacuum,” Borreggine said. “Environmental changes are determined by policy choices and by the political systems that we’re subjected to — by capitalism, by racism, it’s affected by all these things.”

When it comes to climate solutions, “we have to acknowledge that it’s not going to just be about changing the environment: it’s going to be about changing our society,” they added. 

That element of human choice and adaptation had long been left out of the story of why the Greenland colony failed — a story that has often been cast as a parable of human failure to adapt to ecological change.

The fate of the island’s Norse settlements is one of the great mysteries of North American anthropology — sometimes cast as an early version of “lost colony” tales like the disappearance of Roanoke from 16th Century North Carolina.

In the past, in popular works like Jared Diamond’s Collapse, that story blamed the Norse colony on Greenland for “completely failing to adapt to the environment,” Borreggine said.

According to that account, as temperatures fell in the Little Ice Age, the Norse suffered from a “fatal conservatism in the face of fluctuating resources,” according to a pivotal 1980 paper.

This account, however, starkly contrasts the size, longevity and flexibility of the larger Viking colonization project — which seeded long-lived settlements and states from Ireland and Iceland to the river valleys of what became Russia.

The Greenland colonies alone lasted from 1000 to about 1450 AD: about as long as the period between the present day and the earliest English settlements in America. 

Over the past decade, new research has offered a haunting correction to the old story of a fatal Norse resistance to change.

Instead, new archeological finds suggest that for centuries the Greenland Norse did adapt to their new environment — borrowing cultural practices from their Inuit neighbors and rivals, like hunting seal, walrus and caribou.

But as the weather worsened, that adaptation ultimately wasn’t enough to save them, as Science reported in a  2016 survey of the new findings.

The recent research outlined in Science suggests that the Norse colony’s economic base was the sale of walrus ivory back to Europe, which a 2022 study found was sold as far east as Russia.

The worsening weather of the Little Ice Age closed sea passages back to Europe and disrupted the walrus ivory trade — dealing the failing colony another blow.

At the same time, competing sources of elephant ivory from Africa and walrus ivory from the former Norse states in Russia undercut the colony’s economic foundation. 

In addition, they faced rising conflict with the Inuit peoples, who like the Norse migrated across the icy islands of the North Atlantic across the centuries of the medieval period. 

This created an environment in which crisis “was all happening at once, every year,” Christian Madsen of the Danish and Greenlandic National Museums in Copenhagen told Science.

Disruptions from falling temperatures “could eventually have cascaded up through the system,” Madsen said.

The PNAS paper suggests that the rapid sea level rise — magnified by land sinking beneath the weight of ice — was another factor pushing Norse colonies to adapt, retreat and finally flee, Borreggine said. (The idea that the colony left, rather than dying in place, remains controversial among scientists.)

Their timing was ironic: the last Norse settlement in Greenland was empty by 1450 — about the same time other Europeans began exploiting North America’s bountiful, densely populated East Coast.

That is a coastline that the Greenland Norse had been the first Europeans to investigate, Borreggine pointed out. The mythical founder of Greenland was Eric the Red, who was exiled from Iceland for manslaughter — and whose son, Leif Ericson, established the short-lived colonies in Newfoundland in the generation after the founding of Greenland itself. 

But though these colonies stood at a potentially profitable crossroads — at the western limit of an expanding world economy stretching from China to the Arctic circle, and just east of rich, powerful potential trading partners like the nations of North America’s eastern woodlands — they were never quite numerous or connected enough to close that link, a landmark 2011 study in PNAS found.

Their communities were “too small, and too isolated to be able to capitalize on and compete in the new protoworld system extending into the North Atlantic in the early 15th century,” the 2011 study found.

That failure made the Norse both the first Europeans to encounter North America — and the first to abandon it.

Instead, other powers filled that niche. Just as the Norse were abandoning Greenland, Basque fishermen from the French-Spanish border were already harvesting the rich cod banks of eastern Canada.

In the decades and centuries to come, a similar economic model  — one based on the export of other high-value animal products, in this case furs — would form the economic basis of British, French and Dutch colonies in North America.

Their failure in the face of complex crises spurred by climate change echoes the challenge facing modern society, Borreggine said.

But there is one pivotal difference, while we can slow climate change, “they were locked into it,” they said. “We aren’t completely doomed. I’m definitely not a climate alarmist or a doomsdayer. The last takeaway that I want people to get from it’s that we are going to die just like the Vikings.”