I think the best explanation would be to see it the other way 'round : the Trans-Polar aleut is
not some fringe component of the SAIM taking over Greenland and later Iceland. Just as it recently did, Greenland would get independent from Denmark once they figured out they'd better keep for themselves the remaining fishing ressources and the foreseable mining opportunities (the ressources rush in SR timeline being just the good incentive for that).
Then, here comes the Denver Treaty. Athabaskan council is going to get most if not all of Northern America, and is involved in the SAIM just as much as the Sioux, Ute, Pueblo, and the likes. And you have all those inuits and eskimos, loosely tied to the SAIM and spread from Canada to Alaska and Russia. Would the US and Canada leave control of the so-called northwest passage to the Athaskan ? Would Russia leaves part of its territories to a confederation, no matter how loose, whose political center is in Denver, Colorado ? And you have Greenland. At least nominally an native amerindian nation. Plus, it has established diplomatic relations with US, Canada, Russia, Europe, and a government with a prime minister and a parliament, not some fancy tribal council led by feathered shamans. All you have to do is let the US State Department getting creative during the Denver Treaty negociations, and make up a country. They put the capital in Inuvik to make it like the TPA is a North American nation, but Greenland/Thule would be leading the show.
Once you consider Greenland to be the core of the TPA, no matter where the capital is, Iceland joining looks a bit less odd.
QUOTE (DarusGrey @ Mar 4 2009, 10:49 PM)

Still seems kinda arbitrary(I know, it's SR, you have to accept it sometimes

) , collapse of the fishing industry in 20-30yrs wouldn't have as big an effect as that I'd think, following economic trends by 2029 Fishing will only be 10% or less of GDP compared to 80% 40 years ago.
T:WL quotes both the collapse of its fishing industry
and the 2029 Computer Crash as the reasons behind the move. Current figures has fishing products making up to 40% of Iceland exports, so the collapse still wouldn't be good news. The Crash would devastate the rest, especially the banking sector (for that one, just look at what is currently happening in Iceland).