Indeed, it's a multi-stage transparency. I wanted to firm up the boundaries of the ice caps a little, and figured a profile would do the trick. Easiest fix would be to do the caps one at a time instead of both on the same disc, methinks.
Thanks for the info! I'll check out the .pdf tute itself once I feel like I'm done with the chapter, I expect there are lots of nuggets in there based on the great stuff posted above!