A few things come to mind for me with this question. Big bullet in light weight rifle, or smaller faster bullet in light wt rifle.
For Alaska, and in a light weight rifle, I don't think you could go wrong with either a 30.06 or a 338-06. You should be comfortable with either of those with a 20-21" #2 barrel contour custom built rifle with as light stock from lonewolf.
If for whatever reason you felt "undergunned" with either (which I can't imagine why personally), then I'd opt for a 300 saum or 300 wsm.
My 30.06 wears a fluted #3 22inch PacNor. It has the factory wood stock that has been painted and pillar bedded. The bolt is fluted. The scope is a Leupold 4.5x14.40. I could carry this rifle all day long for weeks. Imagine that with a fluted #3 barrel, 20" long and a little 12oz lonewolf stock!
Slam some 180 TSX, partitions, or Aframes, or Northforks in there and anything coming your way is toast so long as you know how to shoot. Stuff those bullets over a powder that gives you top velocity for the 30.06, like Reloder 22, or possibly Reloder 17 (no experience with that one yet).
Here's my 30.06 with a bear from BC and some wolf pups from Ontario:
The trick is, with a 30.06, if you encounter something that scares you or makes you feel undergunned, KEEP SHOOTING!! And aim for the head!!