Viking settlers occupied parts of Greenland from roughly 985 to 1450, farming and building communities before mysteriously vanishing. Why they left has long been a puzzle, but a new paper suggests that one surprising factor likely played a major role: rising sea level.
“There’s been a shift in the narrative away from the idea that the Vikings completely failed to adapt to the environment and toward arguments that they were faced with a myriad of challenges,” said Harvard University graduate student Marisa J. Borreggine, lead author of the study, just published in the journal Proceedings of the National Academy of Sciences.
The departure of the Vikings coincided with the start of the period known as the Little Ice Age, when many parts of the world saw plunging temperatures over a period centuries, and ice sheets took on more mass. While cooling and increased freezing might seem likely to lower sea levels, in Greenland it had the opposite effect.
During the Little Ice Age, as the Greenland ice sheet grew, this led to a process called glacial isostatic adjustment, in which the immense weight of newly added ice pressed the underlying land downward. At the same time, the mass of all that new ice increased Greenland’s gravitational pull on the surrounding waters of the North Atlantic. Both factors caused sea levels to rise along the coasts.
Focusing on the Vikings’ Eastern Settlement from about 1000 to 1450, Borreggine’s group analyzed the effects on known Viking habitations. During this period, researchers found that the settlers experienced up to 3.3 meters of sea-level rise throughout their occupation—two to six times the rate of modern human-induced sea-level rise in other places. Noting the partially drowned ruins of a Viking warehouse among other sites, the group found that 75 percent of known Viking sites lie within a thousand meters of an area of flooding.
“Not only do you have the ground being pushed down, you also have the sea surface going up,” Borreggine noted. “It’s a double whammy.”
“What we were focused on [were] previously unconsidered environmental changes associated with the advance of glaciers proximal to the Viking settlement,” said study coauthor Evelyn Powell, a postdoctoral researcher at Columbia Climate School’s Lamont-Doherty Earth Observatory. “Overall, this study was an inspiring example of the interdisciplinary work that exists in the intersection of geophysical modeling, climate science and the study of the human condition.”
The impact of rising seas was also seen in the changing diet of the Vikings; as seas rose, they shifted from agricultural products to more marine-based foods, perhaps as their fields became saturated with rising salt waters or flooded permanently.
The new study adds to a long-running debate about what propelled Viking immigration to Greenland, and later, their exodus. This includes a 2015 study from Lamont-Doherty researcher Nicolás Young bucking the common assertion that initial settlement was spurred by an exceptionally warm time preceding the Little Ice Age known as the Medieval Warm Period. Young claims that in this region, the Medieval Warm Period actually was not all that warm.
Today, as the Greenland ice sheet melts in a fast-warming climate, sea levels are actually receding. According to ongoing research by another group at Lamont-Doherty, this is happening quite rapidly, as much as an inch a year. This presents a new challenge to inhabitants: modern coastal settlements without access roads depend on already often shallow inlets, straits and coastlines for travel and fishing. This means that some communities could become stranded.
Borreggine noted parallels between Viking time with the modern day—and one major difference. “The Vikings didn’t really have a choice,” said Borreggine. “They couldn’t stop the Little Ice Age. We can do work to mitigate climate change. The Vikings were locked into it.”
Adapted from a press release by Harvard University.
Fascinating hypothesis, with lessons for us. A thousand years ago, the 3.3 meters–essentially 10 feet– of sea level rise over four centuries fundamentally changed Greenland. That was due to natural climate cycles. Now, the human-triggered warming is far faster. With the current rate of acceleration of melting on the Greenland ice sheet that amount of sea level rise could occur this century.
I read somewhere that the Little Ice Age had something to do with volcano eruptions worldwide. And I also read that the Little Ice Age was caused by an exceptional warm period preceding it on University of Massachusetts Amherst site. I heard about this last one before and that it could happen again. The whole thing not very clear as yet, is it? Some researchers still insist that Greenland was frozen when the Vikings arrived. I don’t buy that now. They were not stupid.
There are core samples from the Greenland ice sheet that show crops being grown in the Medieval Warm Period. This runs at odds with the notion that our temperature increase is solely due to humans and is minimized or ignored by climate ’scientists’. As my bother, a geographer said:”There be gold in them there climate hills.”.