Sure, and I'll use the opportunity to disagree with Dr. Lajeunesse a little about what they could do.
In our own north, we have a signals intelligence facility at Alert. We have a radar installation that provides the early warning for continental North America about inbound air threats through the North Warning System, and we have several forward operating locations for our fighter aircraft. Every one of those locations is a potential military target for any particular type of missile that could be fired against a target on land.
The Russians have advanced cruise missiles that can be deployed from either planes, surface ships or submarines, so a submarine could be in our waters doing various things. Among the things it could do would be trying to strike one of those military installations.