I was taught that Leif Erikson led an expedition to Newfoundland over 20 years ago in public school.
"Transatlantic exploration took place centuries before the crossing of Columbus. Physical evidence for early European presence in the Americas can be found in Newfoundland, Canada1,2. However, it has thus far not been possible to determine when this activity took place3,4,5. Here we provide evidence that the Vikings were present in Newfoundland in AD 1021. We overcome the imprecision of previous age estimates by making use of the cosmic-ray-induced upsurge in atmospheric radiocarbon concentrations in AD 993 (ref. 6). "
Seems that before hand the evidence was circumstantial and while everyone was confident it was the case, they can now prove it with better dating techniques.
The species is actually not absolutely crucial in this case. The trees were dated by looking for solar flare activity in the rings; the trees are known to have been cut by Vikings because they were cut with steel tools.
> The received paradigm is that the Norse settlement dates to the close of the first millennium9; however, the precise age of the site has never been scientifically established.
The paper is about more precise dating, afaict, not a revelation that they arrived around then.
"Transatlantic exploration took place centuries before the crossing of Columbus. Physical evidence for early European presence in the Americas can be found in Newfoundland, Canada1,2. However, it has thus far not been possible to determine when this activity took place3,4,5. Here we provide evidence that the Vikings were present in Newfoundland in AD 1021. We overcome the imprecision of previous age estimates by making use of the cosmic-ray-induced upsurge in atmospheric radiocarbon concentrations in AD 993 (ref. 6). "
Seems that before hand the evidence was circumstantial and while everyone was confident it was the case, they can now prove it with better dating techniques.