Greenland, not Iceland. Greenland was still Viking into the 13th c, the cold got worse, and more importantly, the ships stopped coming from Europe. No trees on Greenland to build boats. The population was trapped. One possibility raised in the 1980s (hmm, maybe 1970s) was that German corsairs arrived there and carried off the entire remaining colony.
Thanks for the corrections. The other one I always get messed up on is “Was Greenland really frozen in the old days, and Iceland was green as the Vikings were trying to be tricky, or vice-versa?”
But there were plenty of trees to the west and Newfoundland was closer than Iceland. I think they abandoned Greenland and were ultimately absorbed by the native populations in North America.