Thanks for the ping. I think it was back in 1100 A.D.(?) or so when the Vikings abandoned Iceland(?). They were farmers by that time, and Christian. When the farms died off because of the cooling, the native Eskimos tried to get the Vikings to join in their hunts. But the Vikings wouldn’t join because of all the pre-hunt rituals to the pagan gods. The Vikings died off and/or left.
At least that is one theory I saw on TV. Sounds plausible.
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.