According to the sagas which the Ingstads used to find vinland. Lief Ericson not only discovered North America, but he tried to encourage settlement by exagerating the bounty of the land. The lack of viking settlement may be due to questionable credibility on his part. I believe he or his father fled Iceland as a criminal.
The archeological records show the Basques processing whales on the shores of Newfoundland and Labrador. While I guess it is not impossible that these whalers found Newfoundland via Greenland, Greenlan is a long long sail from northern Spain. But it does make sense that a whaling vessel might end up there as whales were plentiful in the Artic.