It was warmer and then it got a lot colder. Ships stopped coming from the east, and the Vikings did not make the adaptations to cold that the Inuit did which enabled them to continue living there. So they probably want back to where they had come from or sent their children there.
Before it got colder, the Vikings also built at least one settlement in Labrador, in NE Canada.
Archaeologists discovered Viking artifacts in Labrador a couple years ago, which I think I also posted on Free Republic.