Just a thought here, but just a wall of ice won't keep the air in. It would need a ceiling, too. This is because the first law of matter (I think it's the first) states that matter moves from the most concentrated area to the least concentrated area. Therefore, the air would flow upward into space, leaving earth to freeze. And centrifugal force wouldn't hold it in, either, because that only works when the earth is spinning vertically. Like I said before, this is just a thought, and could be proven wrong for all I know.