Also, I would hardly call a single ice shelf evidence of an all-encircling ice wall around the entire world.
Here's a quote following Tom Bishop's
" 'It would be impossible to conceive a more solid-looking mass of ice; not the smallest appearance of any rent or fissure could we discover throughout its whole extent, and the intensely bright sky beyond it but too plainly indicated the great distance to which it reached to the southward.' Two weeks and 250 miles later they had still not reached its end - although at one point it sank to a height of 50 feet, allowing Ross a glimpse from his mast of 'an immense plain of frosted silver' - and with the austral summer coming to an end they dared not risk being trapped. On 9 February they turned for Tasmania."
Therefore, obviously, the entire Earth is surrounded by a 150 foot ice wall.