A Solar Blast From 1,000 Years Ago Could Hold the Solution to a Major Viking Mystery

4 min readHere’s what you’ll learn when you read this story:Figuring out when Vikings first traveled from Europe to North America has proven tricky ever since the 1960 discovery of a Norse settlement in Newfoundland. A tree-ring study appeared to pin down the date of the Vikings’ arrival to 1021 C.E.But new research shows tree rings can sometimes be imprecise, leaving the date unsettled.Cosmic rays may hold the answer to a question that has stumped archaeologists for decades: exactly when did the Vikings first set foot in North America? The evidence is locked in tree rings— so all we have to do is add them up to figure out a date, right? Unfortunately, that’s not quite precise enough of a method to eliminate all doubt.Soon after Norwegian archaeologists discovered the ancient Norse settlement known as L’Anse aux Meadows in 1960 in Newfoundland, they dated it to around 1000 C.E. The remnants of timber-and-sod buildings on the tip of the Great Northern Peninsula marked the first known evidence of European presence in the Americas. Set against cliffs, bogs, and coastline, the UNESCO World Heritage Site continued to fascinate the experts who came to the site to study the Vikings’ migration to the unknown region they called Vinland.Two medieval Icelandic texts, the Saga of the Greenlanders and the Saga of Erik the Red, both tell tales of Viking voyages to Vinland, with Leif Erikson as their central figure. L’Anse aux Meadows contained relics of the Viking attempt at setting up camp in the area, including iron nails and bronze pins, lending credence to the stories. Dating the site is tricky, though, and for decades, “around 1000 C.E.” was as precise as researchers could get. That is, until a 2021 study published in Nature pinpointed the earliest Norse presence in Newfoundland to 1021 C.E.To establish that date, the authors used cosmic rays.Examining evidence from the site, archaeologists discovered pieces of wood that were likely cut down with metal axes, which were commonly associated with the Vikings but unknown to the Indigenous people who already inhabited the region. Because that wood sat in storage for decades, it was still intact when radiocarbon dating capabilities were able to give us a more advanced way of looking at them. Those advances and the realization that cosmic rays leave carbon-14 spikes in tree rings eventually made dating the wood possible. Specifically, Fusa Miyake’s 2012 discovery of how cosmic ray carbon-14 spikes show up globally in tree rings—they are now known as Miyake events—created a new approach to solving the riddle of L’Anse aux Meadows.In 993 C.E., a torrent of high-energy particles struck Earth’s upper atmosphere and collided with nitrogen atoms, producing a sudden surge of carbon-14 around the world. Trees inhaled that radiocarbon, along with ordinary carbon dioxide, and sealed it into the growing ring correlated with that year. As a result, the chemical signature of that 993 C.E. carbon-14 spike can be found in ancient wood from Newfoundland to New Zealand, like a kind of natural timestamp. In any sample of ancient wood that retains its outermost ring, researchers can count forward from the spike to the bark to learn exactly when the tree was cut down. It’s a lot like the trick we teach children for dating a stump, applied with much greater technical precision.The wood cut by the Vikings at L’Anse aux Meadows includes samples from three different conifers with visible rings and a clear outer growth edge. Applying their carbon-14 method, the researchers dated all three samples to 1021 C.E. The cut marks left by metal blades prove that the trees were felled by Vikings, making the samples the earliest precisely dated evidence of Europeans in the Americas. Of course, the Vikings may have arrived earlier, given that the surviving samples of wood might not be the earliest in the timeline of the Viking’s North American presence. In any event, they were undoubtedly centuries ahead of Christopher Columbus sailing the ocean blue in 1492.“We overcome the imprecision of previous age estimates by making use of the cosmic-ray-induced upsurge in atmospheric radiocarbon concentrations in 993 [C.E.],” the study’s authors wrote, adding that their date established a baseline for European awareness of the Americas and the “first known point at which humans encircled the globe.”But it turns out that the story may not be so cut and dry after all. In a 2026 review published in New Phytologist, a team of researchers led by Amy E. Hessl of West Virginia University cautions that individual trees may record carbon differently, contributing to a “blurring” of annual radiocarbon signals.The authors warn against relying on trees for pinpointing past radiocarbon spikes. While these Miyake events often get recorded in trees with “remarkable synchrony,” the authors write, “significant variability between samples remains, limiting reliable use of tree rings as a precise indicator of the timing and scale of past 14C production.”So the debate continues, and the precision of the 1021 C.E. answer to the enduring question may not be as certain as we once believed. But there’s little doubt that Vikings did chop down a few trees in a Newfoundland forest roughly four and a half centuries ahead of Columbus’s arrival in the New World. Whether the Vikings came a decade earlier or later than 1021 is the kind of question that keeps archaeologists arguing and keeps the wood worth re-examining.Tim Newcomb is a journalist based in the Pacific Northwest. He covers stadiums, sneakers, gear, infrastructure, and more for a variety of publications, including Popular Mechanics. His favorite interviews have included sit-downs with Roger Federer in Switzerland, Kobe Bryant in Los Angeles, and Tinker Hatfield in Portland.