Birmingham have signed Nottingham Forest midfielder Robert Tesche on loan.
Goalkeeper Ben Amos has had his loan stay at Bolton from Manchester United extended by a further month.
The teenager becomes the second signing of new Minstermen boss Nigel Worthington, who replaced the sacked Gary Mills at Bootham Crescent earlier this month.
Carson, who has made 31 appearances for Ipswich since making his debut in March 2011, has struggled for game time under Town boss Mick McCarthy but is expected to go straight into York's squad for Saturday's home league game against Port Vale.
Northern Ireland international Carson is well known to Worthington following his days in charge of the national side.