It's only a decision that can be made after discussing with our allies, because if the United States tells us that they will take care of the sea lanes, and that therefore it would be much more helpful for them, when they're doing that role, if we took care of the Arctic, then you're actually helping your own security by allowing your ally to undertake a mission while you do something else. It's a question of burden-sharing.
If the United States, on the contrary, says they don't really see all that great of a threat in the Arctic, but they need a Canadian naval presence off the Horn of Africa and in the Asian Pacific, which would be much more helpful, then that's the kind of policy you might want to pursue.
Those are two different options, but my point is simply that it's illusory to think that we can do both under current budgetary conditions.