AHC: The Irish Colonize Iceland before the Norse

How can you get the Irish (May it be from the High King or some Chieftain's expedition) to colonize and settle Iceland before the Norse before becoming a formidable Maritime force against the vikings and later discover America themselves? When would be the apt POD? Could the other Celtic Kingdoms (Scotland, Brittany or Wales) do this?
 
Lots of scenarios, but earlier the better since that of logistics, unless you write in seeding of trees near the waterways:

"For reasons that are still unclear, it appears that some tree species declined
drastically in the early centuries of the first millennium AD. Elm had been
in decline since 3,000 BC, probably due to a disease that only affected Elm, and had virtually disappeared by the 7th century AD. By this stage too, the early law tracts indicate that the great woods were now confined to marginal land and upland areas."

In other words, later Ireland likely got its wood elsewhere for ships and would unlikely become a maritime power enough to feel expansive to send far flung trading ventures which can get blown off course on the return, like to Northern Spain. Early settlement would not require many to start the process, especially with sheep and cattle ranching, which did take hold with the Viking/Celt slave IOTL.

According to the above article, ship building took off a bit only after all the forests had almost totally died out and the English took over circa 1600, indicating a trend in society that is hard to erase via AH.

Oak seems the main type still existing and some ash, etc., but likely a long haul and not near many rivers.

Of course the Vikings prowl around around the 7th century and onward, but with the church so strong a retaliation strike is unlikely. The church used leather hide ships encased in a wood frame for their early settlement of Iceland IOTL circa 800 AD, but that was really daring of them and probably an act of religious faith. How about a druid act of faith as well, for a very early settlement? Or maybe related to the bogmen executions perhaps? The late could provide some historical evidence to build a story with.

http://news.nationalgeographic.com/news/2006/01/0117_060117_irish_bogmen.html

http://news.nationalgeographic.com/news/2006/01/0117_060117_irish_bogmen.html

 
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