I'll answer that in a relatively simple way. Sailors around the world are going to view the Arctic as open water. As there's more open water, you're going to see more activity from navies. Navies will use the Arctic in the same manner they use any other ocean in the world. In that regard, aside from the Arctic offshore patrol ship, which will be able to establish a presence in Arctic waters, there's going to be a need for enhanced surveillance and communications capability. This kind of capability was already alluded to in your earlier study into the air defence.
The only other capability, not for the submarines we have today but for the replacements I would advocate, would be those having to do with under-ice activities, within the means of the technology of the day. That is going to develop beyond what I could anticipate today, since the decision about that kind of capability would be made a decade hence, but that is what one would want so that others couldn't take refuge under the ice.