One POD would be the 'big' countries (France, USSR, US, etc.) not focusing on Antarctica at all for whatever reason, leaving it to the Southern countries. Argentina, Chile, South Africa, Australia, and so on. In this ATL, no Antarctic Treaty is signed, so they build up bases and prospect for minerals and resources down there. Chile has a civilian settlement--with children!--on the South Shetlands, so it wouldn't be too much of a stretch for them to have permanent settlements on Antarctica proper. Argentina has actually had children born in Antarctica (in 1978), and also has families semi-permanently settled there, so it wouldn't be too much of a stretch for them, either. You could even see a war between them over their claims.
EDIT: Hey, that would really be a nifty TL. (Not necessarily the ice war, though) Too bad I don't really have the time or skill to make it, though.