Sorry, was on my phone for that last post. I'll elaborate more.

The idea is that, theoretically, both arks will glide/break through across the top of the ice. That's the hope anyway. However, we're basically journeying into the unknown, as no one knows what's actually out there, i.e the conditions of the ice amidst the weird magical blizzards, or even if there is ice past the meridian where all exploration into the east has ended. It could all be ocean for all we know. There might be massive glaciers that the arks can't navigate past and we must burn through instead, and who knows what else.

By placing runners on the bottom, do you mean like, at the bottom of the seafloor? Because that would be very difficult and dangerous, seeing as how we're sailing on actual ocean and not frozen over landmasses, so the seafloor would be incredibly deep and yeah. 

The state of the armada that left before (the one that our teachers are part of) is unknown to us at the moment.