"I still need to figure out a map to see how the length of the coast between the north and the south encompasses all this turf and accounts for the difference in temperature."

If you have the northmen using Viking-stile longboats you should also remember to map out the rivers since the longboats are well made for river travelling for example the Vikings traded with Constantinople did go by the rivers

If you are interested in some of the creatures of Nordic folk-lore check out 'humon' on Deviantart - http://humon.deviantart.com/gallery/ - and search for troll, or something like that