So Salted Fish to Greenland (Really? They couldn't catch enough fish there?) in exchange for....?
Hmm.
Perhaps a triangle trade with Europe (more likely Britain)?
So Vinlandic Fish (and mead/other goods) to Greenland
Greenland trades the food for hunting goods (on the assumption that with a food and booze supply, Greenland can focus on hunting polar bears and the like - I don't know a lot about Greenland, so somebody describe what they have to see).
Those goods are shipped to "Europe", where they are traded for iron, etc, and maybe a bit of raiding whilst in port (say stashed in N.Ireland/Scotland/Britain), and then sail back to Vinland to complete the circuit.
Is there a triangle trade route that would work? (I've thrown in raiding because an unpopulated Vinland is a pretty good place to stash your loot with family, nobody is attacking you there any time soon.)