As der Spiegel reports, they might just have gotten homesick -- too isolated from trade, too far from home:
The descendants of the Vikings had persevered in their North Atlantic outpost for almost 500 years, from the end of the 10th century until the mid-15th century. The Medieval Warm Period had made it possible for settlers from Norway, Iceland and Denmark to live on hundreds of scattered farms along the protected fjords, where they built dozens of churches and even had bishops.These scientists looked at the bones left on Greenland -- of the human inhabitants, of their lifestock, and of what they fished.
Their disappearance remains a mystery to this day. Until now, many experts had assumed that the cooling of the climate and the resulting crop failures and famines had ushered in the end of the Scandinavian colony. But now a Danish-Canadian team of scientists believes that it can refute this theory of decline.
They found that, when the warming ended, the Vikings quickly turned to seafood, especially seals. Which makes sense -- no one's going to just starve to death, especially hard-assed warrior types.
The rest of the story seems more speculative, but plausible:
The scientists suspect that a combination of causes made life there unbearable for the Scandinavian immigrants. For instance, there was hardly any demand anymore for walrus tusks and seal skins, the colony's most important export items. What's more, by the mid-14th century, regular ship traffic with Norway and Iceland had ceased.In the end, the inhabitants of Greenland just might have seen no future for themselves there, and returned "home." The lack of valuable tchotchkes suggests the departure was orderly, and not the result of disease or calamity, which you would expect if the climate were failing.
As a result, Greenland's residents were increasingly isolated from their mother countries. Although they urgently needed building lumber and iron tools, they could now only get their hands on them sporadically. "It became more and more difficult for the Greenlanders to attract merchants from Europe to the island," speculates Jette Arneborg, an archeologist at the National Museum of Denmark, in Copenhagen. "But, without trade, they couldn't survive in the long run."
The settlers were probably also worried about the increasing loss of their Scandinavian identity. They saw themselves as farmers and ranchers rather than fishermen and hunters. Their social status depended on the land and livestock they owned, but it was precisely these things that could no longer help them produce what they needed to survive.
The great thing about history is that is it always more complex than we assume. This seems like another example that proves that rule.