After being exiled from Iceland for manslaughter, a Viking known as Erik the Red headed west in search of a new home. The bearded, red-haired explorer ventured 180 miles away, arriving on land that was not yet part of any European settlement. He spotted a green meadow and named the area Greenland, hoping to entice others to come. From about 985 to 1450, a small population of Vikings farmed and built communities on the island’s southern coast. Then, they mysteriously vanished.
Scientists and historians have proposed many theories for their disappearance, from plague, to drought, pirate raids and temperature changes. Now, a new study points to a key factor that may have prompted Vikings to flee their settlements: rising seas and subsequent flooding. The waters around some settlements may have risen by more than 10 feet over four centuries.
“The Vikings were experiencing pervasive sea level rise at the same time as other environmental, social, and economical challenges,” Marisa Borreggine, a doctoral student in earth sciences at Harvard University and the lead author of the study, said in an email. “Several factors coalesced to cause the Vikings to reach a tipping point and abandon the settlement, and now we have a better understanding of the impact sea level change had on their society.”
Sea level rise has previously been considered as an explanation for the Vikings’ disappearance from Greenland. Other calculations have estimated that the nearby ocean rose by a few feet during their centuries of occupation. Farmlands were inundated and land disappeared. But the new study pinpoints the extent of sea level rise more concretely, and details when and how the ocean was rising locally, incorporating advanced sea level models and high-resolution topography.
The new findings show some settlements experienced up to 10.8 feet (3.3 meters) of sea level rise during the Vikings’ residence — what Borreggine believes is one of the study’s most surprising findings. That’s about two to six times the rate of the 20th-century average. About 79 square miles (204 square kilometers) flooded, about 1½ times the size of San Francisco.
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About 75 percent of Viking sites were within roughly 3,000 feet of an area of flooding, the study found. Many ruins can be seen in the region today.
“The environment for the Vikings in Greenland was really, really tough and it was getting worse over the time they were there,” said Richard Alley, a study co-author and geoscientist at Pennsylvania State University. “They’re stuck in these little places next to the sea that are not very big, and they’re losing them because the sea is rising on them.”
Alley said evidence of the rising seas may also be seen in the diet changes of the Vikings, who shifted to more sea-based diets than land-based and agricultural foods.
Local sea levels can change for a number of reasons, Alley said. In this particular case, he pointed to two influencing factors.
First, the Greenland ice sheet near the Vikings was changing, and their land was sinking under the weight of the ice. The Viking abandonment occurred during the climatic shift from the Medieval Warm Period to the Little Ice Age, and at that time the southern Greenland ice sheet advanced and grew larger. Cooler temperatures and the development of ice would intuitively suggest that sea levels would decrease, but previous data and the researchers’ model showed the opposite happened.
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Think of Earth as a very, very slow air mattress, Alley said. When you sit in one spot, the mattress sinks near you and bulges elsewhere. In this case, added ice on the surface caused the land near the ice to sink.
“The land is moving under that changing ice,” he said. “The Vikings were in very close to the ice sinks, as that ice was advancing through the latter part of this current warm period.”
Second, sea levels were also drawn up by gravity from the ice sheet. Alley explained that the ice sheet was big enough that the ocean actually rose near the sheet. The growing ice pulled more ocean toward it and increased sea levels locally.
Archaeologist Tom McGovern, who was not involved in the research, said the study is very interesting and confirms earlier work suggesting that significant sea level rise affected seaside pastures.
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“I think this can be added to the long list of ‘perfect storm’ impacts that affected Norse Greenland after about 1280 or so,” McGovern, a professor at the City University of New York, said in an email.
Paleoclimatologist Boyang Zhao, who was also not involved in the research, said such changes in the climate probably exacerbated other ongoing issues. In his own recent research, his team has found a prolonged drying trend that likely limited land-based Viking food supplies. He said the new paper explores another angle of climate change — from the seas.
“It is almost impossible at this stage to attribute the demise of [the] Eastern Settlement to one particular factor,” Zhao, a researcher at Brown University, said in an email. “All those climate-related factors will be added to all other factors (ivory trade, etc.), and those led to worsened living conditions for the Norse settlers.”
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Borreggine said the multitude of difficulties the Vikings experienced can be compared to concerns we face now, as modern humans experience climate change on top of other social, political and economic challenges. But while Borreggine said the Vikings could not control factors like the Little Ice Age, “We have the chance to mitigate the effects of climate change today.”
Alley said that people today who live near rising seas could learn from the way the Vikings adapted before fleeing.
“They showed this great resilience, this great adaptability to live there through some centuries of sea level rise before they left.”
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