As we have seen already in the short term, traffic in the north—adventurers, people with a desire to trek their way to the geographic or the magnetic North Pole—has been increasing over the last few decades as technology has enabled people to be able to conduct such undertakings.
In the long term, the effects of global warming on manoeuverability in the north is going to be extremely gradual. A good example would be the multi-year ice that breaks off from the polar ice cap and then clogs up some of the transitways. It has, in some cases, a more negative effect than positive effect on transit in opening the sea, at least for the foreseeable future.
Having said that, we will see more people in the north, whether it be adventurers, or folks conducting exploration for resources. As General Bowes has mentioned, it's not a question of Defence, but a question of whole-of-government input and control.