The 32-year-old former Manchester United Midfielder has been signed on a short term contract after being released from Wigan Athletic last summer. He has been training with Salford City FC.
Once tipped as a replacement for Paul Scholes by then coach Alex Ferguson but he fell out of favour and fell down the divisions.
Gibson is the second ex-United player to join the Ammies in the past week, James Wilson having signed on an 18-month deal from Aberdeen last Friday.
Edited by KARL