I don't know what your metric for significance is, but for me it is related to the extent of change of history it causes. A Viking discovery which did not influ

I don't know what your metric for significance is, but for me it is related to the extent of change of history it causes. A Viking discovery which did not influence Columbus in any way is IMO of tiny significance, because whether it happened or not would have made no impact on history. Colombus discovery of America in contrast caused a dramatic change to development of world history. It could be claimed it was one of the major factors in European world dominance which has affected pretty much every society on the planet the last hundred years. I am saying this as a Norwegian. As much as I'd loved the Viking discovery of America to mean a lot it is completely overshadowed by the dramatic impact of Columbus discovery on later world events. Of course there are alternative ways in which Viking discovery could have been important without influencing Columbus. E.g. if they caused significant changes to native American culture, technology etc. But they seem to have had zero influence on native american culture. They were simply too few people to make any sort of influence.