NASA | Warm Ocean Currents Cause Majority of Ice Loss from Antarctica

You can see that happening in this NASA video which shows warm ocean currents attacking the underside of ice shelves. Ice shelves colored red are thicker (greater than 1,800 feet / 550 meters). Those colored blue are thinner (less than 650 feet / 200 meters).

The ice2sea project team behind the new paper will be releasing its projections on sea level rise into the 21st and 22nd centuries later this year.

http://motherjones.com/blue-marble/2012/04/antarctic-ice-melting-below-warming-ocean