The GrIs is melting along its edges so fast that it is going to leave the outlet glaciers low and dry. Pretty soon we are going to be seeing giant waterfalls flowing out of the ice sheet. Ever wonder how those squared-wedge inlets were formed? Giant waterfalls from a great height. The GrIS doesn't have the height now that it had back in the days when the Laurentide Ice Sheet existed, but waterfalls will form, and out the water will flow. You can forget all the fancy calculations being made based on the glaciers' outflow rates and the sizes of the outlets -- they won't even be around, and they won't matter when the water is flowing straight out of the ice all the way to the top and everywhere in between.

Image from this site (images updated daily): http://www.seaice.dk/iwicos/latest/