a fire that thawed down through the ice?

A fire wouldn't burn all the way through a 1 ft high snow bank, but it would melt snow or ice, create a concave pit and extinguish itself.

If you build a fire on top of ice, it will melt the ice underneath it and sink down into the ice or "through" the ice (another of those troublesome English prepositions). If they used driftwood for the fire, they must have been near a body of water, a lake or the sea. If the ice they built the fire on was over unfrozen water and was thin enough, the fire could melt through the ice cover and fall into and put itself out in the unfrozen water below. If the ice was thick and there was no water underneath, the fire might melt down through the ice a ways and put itself out in the meltwater underneath it. And possibly least likely, it might melt down so far thru the ice that they couldn't see much if any of the light from the fire anymore and had to eat in darkness.

I gather you're still working on "Call of the Wild"

Thank you both.

How would this be a "troublesome" use of through anymore than "drill/auger/cut through the ice, MJ?

A chain saw, an auger, a drill or any similar tool goes down into the ice and then finally through ice.

There's simply an ellipted 'and'; "... melted down and through the ice".

Cool! JTT.