I think this is a definitional thing. If it’s made of salt water, that’s called sea ice which is formed when water just freezes on the surface of the ocean. An

I think this is a definitional thing. If it’s made of salt water, that’s called sea ice which is formed when water just freezes on the surface of the ocean. An iceberg on the other hand is a broken off piece of glacier, which is ultimately made of snowfall, and therefore should always be freshwater (at least on earth!)