But I do disagree with this. Ranger is a light, fast moving warrior with hit and run tactics. Regardless of terrain, the ability to move quickly and stealthily is the rangers deal. Arctic means hide armor, not heavy armor. Ever touched metal in freezing weather? It would be avoided. It's a heat sink, even if you have padded underneath. And believe it or not, stealth is just as applicable in the snow as anywhere else. Just ask the 10th mountain division (who borrowed a lot from the Norwegian fighters in WWII). Also, I don't see how a mountain or hill ranger would use a great weapon over the traditional weapons. Light and being mobile are important, and huge weapons are heavy and slow.
I've done enough road marches and tactical maneuvering in the army, in all environments, to know that it's not just forest that would lend to lighter armor and weapons.
Edit For example, the plains Native Americans didn't use heavy weapons. They were still very much focused on light weapons and mobility.