Yes, the Arctic would be a good location.
You mentioned the action against Iran and Syria. The thing about the new long-range cruise missile that surprised the international community was that it was not necessary for Russia to use that cruise missile against Syria, because it was designed to evade air defences in a much more powerful country. It was, then, almost a demonstration for effect; it was perhaps a demonstration to show that it has a long-range precision cruise missile that could be launched from Russian waters, from submarines, from bombers, and also from ships.
To defend against that, you would need to have a detection capability, which could involve AWACS, could involve the F-35, which I believe has a detection capability against cruise missiles, and could involve land-based sensors. The problem with any aircraft designed to detect against cruise missiles is that you have to have it flying all the time, so it's not really a long-term solution.
Potentially, the RADARSAT Constellation could look down and detect cruise missiles. RADARSAT Constellation is designed to detect ships and so is much more powerful than a satellite higher up; thus it could potentially detect cruise missiles. Also, unmanned aerial vehicles.... I think I mentioned the Global Hawk, which is basically the U-2 replacement—you'll remember the U-2 from the Cold War—which can detect cruise missiles.
If you are looking for persistent surveillance, then you're looking at satellites, high-altitude unmanned aerial vehicles, or a land-based system. Of course, if there's a lot of land, it's hard to decide where to put it.