2. If it *all* went, it would add about 20 feet to sea level.
That also ignores the impact of removing that much weight from the greenland land mass. I don't know if there are any educated predictions on what that impact would be, but my grab-ass intuition is you can't just remove so much mass without greenland itself shifting upward, with some kind of non-zero tectonic consequences.
Melting ice is currently causing Greenland to rise by 3 cm a year. This rate is accelerating, and if the entire ice sheet is to disappear, the island would rise about one kilometre, new GPS readings reveal.