@Ranger30-06: I'm not going to spend the day crawling the internet to prove you don't know what you're talking about. Cadzow shot the Polar with a .223. The Inuit have been using the .223 on brown, black and polar bears for decades. NO ONE who lives in the wilderness or an Alaskan village where they pay $13 for a gallon of milk is going to carry or let alone have access to .458 SOCOM or any other "exotic" round..... It's a question of logistics.
In summary, @Robert B: Your .40 S&W will do the job. Train with your handgun, use a well made bullet and be confident in your equipment but above all, stay aware of your surroundings.