Once Upon a Time in the North by Philip Pullman (2008) Doubleday Childrens

Lee Scoresby is a Texan, and an aeronaut.  He’s won a balloon and is learning to fly it.  He floats into the far north and lands on an island and finds three corrupt enemies, including a killer who is his nemesis.  He forms an alliance with the armored bears to help him win an old-fashioned gun fight.  You meet them next in The Golden Compass.