The way I was taught it oh so many years ago in school, was that Christopher Columbus knew there was land thataway (waves in a westerly direction) due to the fishing fleets working the grand banks and Newfoundland coasts from England.
He, Christopher, was looking for a southerly rout around that landmass to the orient.
Yeah, uh, the Gascon and Basque fishermen used to fish the Grand Banks, and that came about because of the uptick in demand for fish during the Middle Ages, I think that detail was due to the "eat fish on Friday" rule the Pope had made to alleviate famine somewhere. The fisheries kept moving on them (sometimes that's attributed to, you guessed it, climate change) and they went more and more distance from You-rope. My speculation is that the Basques are a language isolate because they originated in North America, possibly settling in Iberia as recently as the 5th century AD.