When 3 feet of snow stand between you and enough soil to dig a proper cathole, the good backcountry citizen packs it out--everything. Use a zipper-lock bag as the poop sack and smaller plastic bags for picking up "mitt style" each of your deposits. Store the poop sack in a nylon stuff sack to avoid accidents in your pack. icy temps should quel the smell until you can dump the contents in a pit toilet or RV dump station. Then dispose of the plastic bags in the trash.