I think a lot depends on your coop and how many chickens you have to determine poop density. Do you use droppings boards? Is it a tiny elevated coop or a walk-in on the ground? What kind of floor does it have, dirt, wood, linoleum, or something else? What, if any, bedding do you use? I don’t know what kind of weather you’ll have in Juneau throughout the winter either. Does it freeze solid until March or April or, being on the coast, will you have days it thaws out? These are the kinds of things I’d consider when making my decision on what to do.
In general, there aren’t any health problems with frozen poop. Since it is frozen, it’s not giving off a significant amount of moisture so once it freezes it’s not a frostbite concern. When frozen it’s not being digested by microbes so it’s not giving off ammonia. Once it is frozen the chickens are not tracking it around or getting it on eggs if they are still laying.
It’s when it thaws that you have issues. It can quickly become a wet stinky mess. That’s the time I’d be concerned, when it thaws.