“If fills up the same volume that it displaced.
Think of a glass full of ice, topped off to the rim with water.
When the ice fully melts, there is no increase in the water in the glass. The level stays the same.”
Correct. Only with a glacier it is like adding more ice cubes to that glass.
Because that ice shelf is already floating, there would be no effect on ocean levels.
They always bring up the supposed danger of the glacier when the real concern is the ice shelf itself. If it were to break off, then it would allow the glacier to slide into the ocean over the course of one or two centuries....That of course ignores the fact that another ice shelf would likely form and halt the glacier slide.