They are able to survive in the tundra by using their larger head crest they are able to heat the air before they breath it in like many ice age animals. His crest would also enable the to break through ice and dig for the bnarbras that they eat.
Another adaptation it would have to either have a very thick fat layer or it is a warm blooded creature, it is most likely the first one because the jade barroth is a reptile. Or it has developed a system to pump blood very fast throughout the body to keep warm internally, this coupled with that snow is an excellent insulator, would keep it warm on the inside and the snow is not practical in hunting and regular barroths mud would keep it cool.
A third adaptation is the spines on his back and tail, which the jade and common barroth share, the spines are there to hold the mud/snow in place and as they are not used in any attacks.