The Role of the Antarctic Circumpolar Vortex & Ocean Current in Keeping Antarctica Frozen
The Antarctic Circumpolar Current keeps the warm waters away from the higher latitudes because Antarctica is disconnected from other land masses. This in turn amplifies the westerlies and therefore, polar front Antarctic Circumpolar Current prevent any warmer air/water to enter the high latitudes of Antarctica.[more on this: wikipedia]

During the Oligoncene/Eocene boundary about 32 million years ago, the Tasman Passage opened which gave rise to the onset of Antarctic glaciation [more on this wikipedia]