In certain embodiments, a transcritical refrigeration system provides refrigeration by circulating carbon dioxide (CO2) refrigerant through the system. A flash tank of the transcritical refrigeration system is operable to supply the CO2 refrigerant, in liquid form, to a low temperature refrigeration case and a medium temperature refrigeration case. A low temperature compressor is operable to compress the CO2 refrigerant discharged from the low temperature refrigeration case. A medium temperature compressor, a parallel compressor, and an ejector are each operable to compress the CO2 refrigerant discharged from the medium temperature refrigeration case, the CO2 refrigerant discharged from the low temperature compressor, and/or CO2 flash gas discharged from the flash tank. A gas cooler is operable to cool the CO2 refrigerant discharged from the medium temperature compressor and the parallel compressor. A controller is operable to dynamically adjust a pressure set point for the flash tank.