the sea ice extent in the antarctic could have something to do with the conveyer process that starts there. As the sea water starts to freeze in winter, ice starts to crystalize and forms long "tendrils" below the surface. Now, i'm not sure how the rest of this works but as the tendrils form and grow, briny water heavy with salt starts to fall to the depths, eventually forming a vast waterfall of extremely cold, salty water that's something like the equivalent of 2000 niagara falls. This massive loss of salt from the surface waters allows the sea around antarctica to freeze more easily and more completely.
Add to that the fact the southern ocean is rarely ever still. It is constantly being stirred around antarctica by winds which makes it more difficult to heat up as the action of the water helps dispel the heat back into the air. Thus, in combination with the loss of salinity in winter makes it fairly reasonable that the antarctic ice would defy the climate models.