heck, at -50 everything will be frozen rock hard, including you if you are not careful. even steel gets more brittle down that low. keep the handles in where they are warmed when not in use. it's deceptive. it can be way below zero with no wind and the sun out with zero humidity and you can stand there without a jacket quite comfortable, until a wind comes along to remind you that you are mostly water. fingers, toes, ears and noses go first. of course during the winter you do not get a whole lot of sun. i'd opt for a through tanged wood handle myself, a full tang with exposed metal might be a bit chilly.
p.s. - i've been there on the pack ice when it was -50F, you don't want to do anything that makes you sweat either, like chopping. the moisture freezes then you do too. had a shipmate who was a deckie, he was out on the bridge wing on our icebreaker one watch & it got that cold. his moustache froze and snapped off on one side. hilarious. i was an engineer, so i got to stay indoors mostly, where it was warm. unless the spray started freezing topside, destabilizing the ship. then we all (including the captain) took turns breaking it off with baseball bats and axe handles. a turn outside was maybe a half hour before you started to freeze up & had to go in.
edited: i see we all said just about the same at just about the same time; GMTA!