...The Alaska Dept of Fish and Game has several links to firearm effectiveness for hunting. Of note is that pump action 12 gauges are very commonly used by their agents, at least around population centers (Anchorage).
So, after years of enjoyable cogitation I decided that a "powerful as you can effectively shoot" semi auto (think 10mm or 45Super or 460 Rowland) with at least 10 rounds in the magazine is a good answer...
Many years ago when I was working for Uncle Sam in the lower 48, their "officially approved" bear defense weapon was also a 12 gauge pump, loaded with slugs IIRC. Unfortunately, the management I worked for during the 3 years I spent doing field work in "the middle of nowhere" Montana, Idaho & Wyoming did not approve of employees carrying firearms, either government issued or privately owned. (And for frosting on the cake, the agency motor pool would not put winches on field vehicles, because they thought winches made it more likely that their vehicles would get stuck. ;^)
Later, when I worked for a different agency out of an office in Colorado, 12 gauge pumps were again
theoretically approved & available for bear defense, but
only if you got approval to attend & completed bear defense training. Funny thing - the training was treated like a perk or award, so folks who never left the office would get approved, while people who spent several months every year in bear country never got the training (& therefore remained unarmed).
I mention all of the above to highlight a simple fact - we live in a world that is far from perfect. A lot of discussions of bear defense tend to drift towards theoretical ideals (caliber, capacity, projectile design, etc.). Out in the real world, some employers or land owners may prohibit certain types of firearms (or all firearms) in bear country, or individuals may not own firearms commonly recommended for bear defense. If you're dealing with such restrictions, should you leave your 'inadequate' .38 revolver or .45acp 1911 at home? Apparently some people might, even though evidence strongly suggests that any gun is better than no gun.
As noted above, "to each his own!"