Identifying Scandinavian y-chromosomes would seem to be the real problem here. For several hundred years the gene-flow was from Ireland to Scandinavia, so a reverse gene-flow from Scandinavia would simply be invisible.
Would this be one of those kidnapping the womenfolk & taking them back home kind of things? Maybe there's some history that I'm missing, cuz I hadn't heard about a male Irish to Scandinavia movement.