Im also interested in an answer to this question.
With each opportunity comes difficulty. Just guessing here but I would say it would be totally possible to melt the snow or ice from a river providing you have the wood (and later perhaps a different source). However what wood will be a available in a frozen wasteland? How much will be available? Will it be dry? All important questions because if you only have a little wood, then you can only melt a little snow and wood will not burn forever. We will just have to wait and see the details on this along with many other such questions.
Ahh, but what if the wood is not the fuel source? What if pteroguin blubber is my fuel?
Really we have no way of knowing until the devs inform us, but I wanted this question to be out here because I really would like to know what sort of depth is going to be in the crafting system.
I do thank you for your response Sullen.