I was referring to the melting of the part underwater.
The part of the glacier that is in the ocean is taller than the water level. As long as this part of the glacier is resting on the bottom, any melting of the ice above the water line will raise the level of the ocean.
Furthermore as long as the glacier continues to flow into the ocean faster than new glacier is formed, the level of the ocean will rise.
If you keep adding ice to your drink faster than you drink the liquid, the drink will overflow.