Yes, with animation it would look as if something is moving in the ice/snow, but I doubt if that's the effect I want. Still, you won't see it in stills, I think, it's just another hue across the other hues on the surface. There is no depth in TG, even not in water, that's just calculated from the surface colors with a refraction angle where the water is a certain distance above terrain (that's my idea anyway).
Here's another iteration, slowly getting fed up with it again, so I might consider something else again to sharpen my knives on. The position of the planes wings and the watery meltholes are bit badly mixed, so I might fix that as a last one.
