What's the noun for firn? Here's the word you're looking for.
firn
A type of old snow which has gone through multiple thaw and refreeze cycles and thus is made of numerous small icy grains, though it is not nearly as saturated with water as snow-cone slush is; can be hard or somewhat soft depending on recent and current weather conditions.
“In the high alpine regions, climbers often encounter firn, a unique form of old snow that has undergone multiple thaw and refreeze cycles, resulting in a granular texture resembling tiny icy grains.”
“Combine such dense firn with a daily rhythm of freeze and thaw, and spring avalanche danger is easy to predict and avoid.”
“Changes in the Earth's surface albedo are a useful indicator of firn pack loss and glacier retreat.”
firnification
The production of firn by recrystallization of old snow
