well never hunted the arctic, but have hunted down to -25 C with my remington 700 30.06... now i have never shot at a polar bear, but have stopped a chargeing black bear in its tracks with a 30.06, so i would say 30.06 will definately fit the bill as a multi purpose gun... now if i was looking for a gun more for survivial up there, i would say something fast shooting, and reliable in the cold, like as you said a lever gun, but as others have said something with ammunition available... so maybe a browning blr in say 30.06. would stray away from semi's and pumps...