Six years ago, a couple of archaeologists discovered the remains of a settlement in a wind-blown area on the northern tip of Newfoundland. The eight wooden structures at the site resemble Viking buildings in Greenland, and the archaeological artifacts found there—including a bronze cloak pin—are definitely in Nordic style.
Scientists now believe that this place called L'Anse aux Meadows is inhabited by Vikings from Greenland. To this day, it remains the only final Viking site in the Americas outside of Greenland.
But there are still many questions about L'Anse aux Meadows: who has solved it? Why? And, perhaps most importantly, when was the site occupied? Determining the age of settlements has always been a challenge-radiocarbon measurements of L'Anse aux Meadows artifacts span the entire Viking era, from the end of the 8th century to the 11th century.
But in the results published in the journal Nature on Wednesday, the scientists came up with new answers to what they believed to be the mystery. By analyzing the rare solar storm marks in tree rings found at Canadian sites, scientists decisively determined the time when the Nordic explorers were in Newfoundland: 1021 AD, or exactly 1,000 years ago.
Michael Di, a geoscientist at the University of Groningen in the Netherlands and author of the study, said that it is important to know more precisely when the Vikings lived in L'Anse aux Meadows.
"This is the first time to cross the Atlantic Ocean," he said, adding that determining the exact date helped mark a turning point in the history of human movement on Earth.
To more accurately determine when the site was occupied, Dee and his colleagues analyzed three pieces of wood from L'Anse aux Meadows. Each piece is from a different tree, still with a skin, and cut cleanly with a metal tool (probably an axe). Margot Kuitems, an archaeologist at the University of Groningen and a member of the team, said it was a gift of wood split by the Vikings.
"The locals don't use metal tools," she said.
Back in the laboratory, Kuitems cut a small amount of wood from each annual ring of each piece of wood. She said it was like splitting hair. "I used a scalpel, but sometimes it was even too thick."
Studying these samples—each sample represents a year of tree growth—the team separated the carbon from the wood. All of this carbon originally came from the Earth’s atmosphere.
"It involves photosynthesis," Dee said.
The vast majority of carbon in the atmosphere is carbon 12, which is a stable atom with six protons and six neutrons. Only a small part is radiocarbon 14, also called radiocarbon. When cosmic rays-high-energy particles from the sun or outside the solar system-interact with atoms in the Earth's atmosphere, carbon isotopes are produced.
Scientists who study cosmic rays used to believe that these particles arrive with a relatively constant barrage, which means that the ratio of carbon 14 to carbon 12 in the atmosphere remains basically stable over time. But then in 2012, researchers discovered two cedar trees in Japan, which recorded inexplicably high levels of radiocarbon in the annual rings from 774 to 775 AD. This peak is now called the Miyake event because of its discoverer, Fusa Miyake Nihon University, a cosmic ray physicist in Nagoya. Since then, other Miyake events have been discovered in tree-ring records, but they are still extremely rare.
"Currently, in the past 10,000 years, we have only three or four," Dee said.
But another Miyake incident happened in the Viking era from 992 to 993 AD. At that time, trees found around the world recorded a rise in carbon-14, and the wood found at L'Anse aux Meadows was no exception. To determine the age of the only confirmed Viking settlement in the Americas, Dee and his colleagues turned to an unlikely combination of dendrochronology (the study of tree rings) and astrophysics.
"We realized that this might change the rules of the game," Dee said.
The researchers found that their three pieces of wood all showed a significant increase in radiocarbon, which started 28 years before their skin. The team concluded that ring 28 must correspond to the year 993 AD. They excluded previous and subsequent Miyake events based on the ratio of carbon 14 to carbon 12 measured in wood, which has changed in known ways over the centuries.
The date is now fixed on the internal annual ring, "All you need to do is count until you reach the forefront," Di said. The researchers calculated that all three pieces of wood analyzed by the team were felled in 1021.
Stuart Manning, an archaeologist at Cornell University and director of the Cornell Annual Ring Laboratory, said that so far, estimates of when L'Anse aux Meadows will be occupied are largely "guess" and he has not participated. This research. "This is hard and concrete evidence related to a year."
But L'Anse aux Meadows has not given up all its secrets. There is more to be learned about its Viking residents. University of Colorado Boulder, a historian who specializes in northern European literature and culture, Matthias Nord Wig said that he was not involved in the research either.
"What's the point of it?" He asked about this website. "Where did they go from there?"
c.2021 New York Times Company