FWIW, I heard from a friend that Canada was having its difficulties with it all during the Cold War because we had no subs that could track or engage either the USSR or the US. They of course knew that and used the passage quite freely--being wary of each other because we had no way to stop them anyway.

That makes sense. Due to the frozen surface, the subs have to be nuclear. Non nuclear subs require regular supplies of O2, and the only way to do that is to surface. Therefore, diesel subs were out. Nuclear subs can stay surfaced for months at a time. (Shanghaiceltic was a submariner, and he could explain this much better than I ever could.)

The situation prompted Ottawa (I think it was Axworthy) to say that they would build ten nuclear subs, That never came about.