My comments on the Humboldt glacier were to point out that the ice sheet is not of even thickness. That if it averages 5000 ft thick, but also has areas that are a mere 200 feet thick, that means all the more ice in other areas.

And if I had never mentioned the Humboldt glacier, but had merely said "y'know, 5000 being an average, that means there is still an even greater elevation of pure ice -- 5000 feet high and twice the size of Texas --- I would have been saying the same thing.

If you want to subtract the areas of Greenland that are, as you say, 1000 ft below sea level, that's fine, It still means the elevations of pure ice are at 4000 feet and twice the size of Texas.

But if I grant you that some of Greenland is 1000 ft below sea level, let's not forget that a substantial amount of it is at Rocky Mountain elevations. Probably more than is below sea level.

And that below sea level thing? ...that, and the movement of ice is exactly why many say (and probably quite correctly so) that even if in a worse case scenario ALL of Greenalnd melts, MUCH of that fresh water will stay put in some GI-NORmous "Great Lakes".