Greenland

     Greenland holds about 10% of the world's ice.  If it all melts, sea level would rise 6-7 meters (20+ feet).

     Greenland ice growth began almost 10 million years ago and reached roughly current levels more than 2 million years ago.

     Over the past 2 million years, ice sheets repeatedly grew and shrank across Canada, the northern US, most of Siberia, and most of northern Europe.  We call these periods Ice Ages.  At their peak, these ice sheets held twice as much ice as Antarctica does today.  (See Hansen 0913 on Overviews page for a geologically recent history of sea level.)  From 20 to 8 thousand years ago (KYa), those ice sheets vanished, raising sea levels by 1 meter per century, including 1.5 meter per century from 15 to 8 KYa.  

     Some researchers (Robinson, Koenig) have made the case that current CO2 levels are incompatible with continued existence of the Greenland ice cap or sheet, especially once temperatures increase to those associated with past CO2 levels this high (~ 400 ppm).

     Perhaps 20% of Greenland's ice is grounded below sea level.  But most of that is inland sea, not connected to the ocean.  Maybe 5% to the ocean.