The Wales internationalist made 28 appearances for the Pittodrie club after arriving from Blackburn Rovers 18 months ago, but has been unable to displace Jamie Langfield his season.
Duncan Fraser, the Aberdeen chief executive, said on the club's website: "Jason made it clear he was keen to return to England and continue his career. He is a proud member of the Welsh international team and, in order to maintain his place in their squad, he feels it is vital for him to be playing every week.The club wish him all the best with his future career."




