Repair and improvement work is being carried out to the 580 car parking spaces in the Wellgate.
Contractors Castle Group started work on the upgrade on Monday.
It is intended to provide a much brighter parking environment, with significantly clearer line marking and more visible spaces.
The car park is to remain open throughout this second phase of the work, which should be completed by the end of the year and is expected to cause minimal disruption for customers.
Peter Aitken, centre manager, said: “This phase of repairs, which will be carried out from now until Christmas, will make a real difference to the growing number of people using the car park.”