Greenland Ice Sheet Losing Mass
I have a Science reference for you; abstract looks interesting:
Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow
This is the mechanism that Hansen's worried about for ice-sheet collapse/disintegration; lubrication by meltwater of the ice flow zones.
The first article doesn't say much, the second leaves out an important fact: thick glaciers on Greenland don't percolate meltwater and are primarily geothermally heated. Their case might be made for the thin edges, but it's irrelevant for the bulk of the ice sheet.