The ice melting from the centre is impossible, I think.
Since warm things fill more than cold things, so it's quite impossible for the wall to be so tall, and yet the melted water flows around down below.
So a 20ml of warm water fills more than a 20 ml of cold water in a cup?
When the water melted, it would flow over, and the more of it melted the more would flow over, so today; we would have ice in a ring around, and inside this ring there would be water, water and more water.
It would flow over like so:
We should all live underwater, according to that.
Eh, when you melt a puddle of ice, what happens? The contraction of ice due to melting makes spaces for water to fill. In the end, it becomes a puddle of water rather than ice. Hence, equilibrium.
However, in such a large scale of the FE, sublimation has to occur at least a few % (such small percentage is huge difference). Sublimation occurs when temperature and pressure falls below the triple point (water). Some parts of the icy layer sublimes into water vapor, which leaves more space for water to fill. Thus, the elevation of sea level decreases, rather than maintaining the same height as in the beginning. Equilibrium is STILL achieved, because, for example, if the total amount of H
20 is 3, then liquid water will be 1, ice will be 1.5, and water vapor will be 0.5.
Sublimation increases more space for the additional volume of water to fill, thus water doesn't bulge. Moreover, evaporation further converts water into water vapor, stabilizing the system.
The ice wall doesn't increase in height; the ice above its mountain ranges is left by the melting process occurred several billion years ago. The surface of the ice wall is not flat.