Let's just say "amateur planetologist"
i.e., I neither shy away from giving the obvious short answers to over-simple questions, nor from admitting that I haven't answers to the more complicated ones -- but I do wish to learn.
Here's something from the British Antarctic Survey.
But...
Here's something else from them, via the BBC:
Professor Chris Rapley, director of (Bas), told the conference that Antarctica could become a "giant awakened", contributing heavily to rising sea levels.
Melting in the Antarctic Peninsula removes sea ice that once held back the movement of glaciers. As a result, glaciers flow into the ocean up to six times faster than before.
The other region in the continent affected by the changes is West Antarctica, where warmer sea water is thought to be eroding the ice from underneath.
I should have thought about the sea ice acting as a dam, having just seen the NOVA about the Missoula Lake floods and the Washington Scablands.