Great idea! I´d say that the key point for the ice parts is flatness, so you might consider getting XPS for the core part, painting the surface white, and then applying a sheet of adhesive, transparent plastic to it, which will give a little depth to it and a glossy sheen as well. Or just use foamboard, paint overall white, and gloss varnish. I´d just leave any "rough effect" to piles of snow, although ice can be rough as well if crumbled, it just doesn´t look "icy" when you model it like that.
As for the sub, I assume you´re talking about Knoxville´s excellent Antarctic Base table which he made for Tactica this year. I don´t recall the exact title of the thread, but you could search the workbench forum for entries by the user "knoxville", or visit this site which has some pics of the table "in action":
http://hamburger-tactica.hq-cooperation.de/pages/fotos2007.html