Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 153; Flight Crew Total 12802; Flight Crew Type 9238
Other / Unknown; Confusion
Ground Event / Encounter Other / Unknown
General None Reported / Taken
Weather
Upon arrival to Des Moines; there was no communications regarding which gate to park. Our gate was occupied; adjacent gate was occupied by one RJ but no-one was out there to receive the airplane in the second space. Turns out the bridge had broken and it was being repaired before our arrival however; it was not repaired in time. Someone failed to take the initiative to have a backup plan in place in the event the bridge was not available by our arrival time. Finally; we saw activity to guide us to Gate XY. The ramp area at Gate XY was snow covered however; part of the lead-in line was visible. We parked; set the brakes; turned off the seat belt sign; ran the parking checklist; received signal to release brakes. Very shortly after; the airplane started to slide! Apparently; there was ice on the ramp under the snow. After brake release; because of the ice and the ramp was not level; the plane just took the chocks with it in the slide. I received the frantic signal to set the brakes and noticed out of the corner of my eye the bridge going backwards to try to get out of the way. Then; I was told we needed to start engines to reposition the plane. Seatbelt sign back on; announcement made; engine start; slight reposition; engines off; seatbelt sign off; announcement; checklist - continued to remain in my seat until all passengers deplaned just in case it happened again.It appeared that the ramp personnel were pretty young and I know that they were doing their best however; because there was no contingency plan in place for parking this plane; the ramp was not properly prepared to safely receive the aircraft at Gate XY (cleared of snow; ice and deiced). Later; I was told that ramp services had been farmed out to a 3rd party operation. It seems that additional training/information needs to be considered regarding a properly prepared safe parking area especially; with winter type operations. We were lucky; no-one was injured and nothing was damaged. Action must be taken to maintain a high priority for safety.
Air carrier Captain reported the aircraft blocked in; shut down; and was chocked at a backup gate is DSM. There was snow and ice on the ramp and after brake release the plane slid backwards taking the chocks with it.