A team of multinational scientists found that the vast amounts of water melting off Greenland's glaciers in recent seasons have inundated this spongy layer in places, filling it up beyond what it could absorb. Solid icecaps have now formed over much of the firn at certain elevations, making it impermeable to additional melt-water. That new melt-water has nowhere to go but off the ice sheet and into the ocean, once again help to rise sea level.
The Greenland Ice Sheet was in terrible shape last season. For the first time since 2012, melting occurred on more than 50 percent of the sheet, and the melt season lasted 30 to 40 days longer than average, according to the National Oceanic and Atmospheric Administration's (NOAA). "If the Greenland Ice Sheet were to melt away completely, ocean level would rise roughly 23 feet" - noted by NOAA. So scientists have good reason to watch Greenland melt closely.