I think any Antarctic outposts would be abandoned once they stopped getting resupply from the outside World. I was going to mention a possible evacuation of allied nations' settelements by the RAAF / RNZAF but Targan beat me to it.
I actually wouldn't be surprised if sucn an evacuation also agreed to take scientists from Soviet / Warsaw Pact nations...I think the ethos of the Antartctic explorers would be such that those from the allied nations would not wish to see their former colleagues abandoned even if their countries were now enemies. Alternatively, scientists from Pact nations might be evacuated to somewhere in South America?
Either way, I see the Antarctic abandoned by the end of 1997 at the latest.