Many existing theories suggest that zombie blood must flow through the body in some manner. ZRS Researcher Kate Steinem started with this baseline when looking into the commonly held belief that the undead freeze in cold weather.
First she observed that a zombie with flowing blood probably functions much more like a cold blooded animal, than the warm blooded human it used to be. From there she found startling evidence of creatures with cold blood surviving in extreme cold temperatures that would turn a living person into a hardened block of ice in a matter of minutes.
“Several species of cold blooded fish have a special substance in their blood, glycoprotein, that acts like anti-freeze to help them survive very cold water temperatures.”
Glycoprotein depresses the freezing temperature of blood sufficiently to render the body immune to the cold. Much like a bottle of vodka in a freezer box, while everything around it is frozen stiff, the vodka never changes from its liquid state.
Steinem argues that if the undead body is able to produce glycoprotein, or something similar, it would then have a workable system that no longer needs to regulate internal temperature to function. Though zombies would still likely move more slowly in extreme cold, their blood would never convert into a solid, continuing to flow and power the body.
Great. Just when I thought my escape plan to the arctic circle was fool proof.