The problem is mostly the huge glaciers in Greenland and Antarctica.
Recent studies indicate that the Greenland and Antarctic ice sheets are gaining mass. It is speculated that warmer temperatures will increase snowfall in those areas, more than offsetting increased melting.
http://www.sciencemag.org/cgi/content/abstract/1115356v1http://www.sciencemag.org/cgi/content/abstract/308/5730/1898 
