Maxwell's Demon could make the atmosphere behave in any way you like, including making the air stay on the 'Flat Earth' whatever. Indeed, no need for the Ice Wall, just station an army of Demons all around the 'perimeter', each of them armed with a microscopic tennis racquet, and instruct them to knock any straying air molecule back towards the disk.
Sadly, Maxwell's Demon doesn't actually exist. If it did, we could have an awful lot of fun with the no-longer-valid Second Law of Thermodynamics, like un-scrambling our eggs; or turning sausages back into live pigs, etc. etc.....