As to why the 1960s and early 1970s should be so cold in the Arctic, it should be noted that it was on the Russian island of Novaya Zemlya deep in the Arctic that most of the powerful Soviet H-bomb tests were conducted in the atmosphere during the huge Soviet test series of 1961-1962, these tests being particularly large and dirty, the largest blast there being a mammoth 60 megatons on 30th October 1961 [11]. The cold plunge in Arctic temperatures occurred in the immediate wake of these tests, and it took about 12 years or so for temperatures to recover to their earlier levels. It is a strong possibility that the two events are connected.
Remember how we used to worry about nuclear winter? Maybe we should just set off a few atomic bombs in unpopulated areas of the globe, if we want to solve the global warming problem.
There is "good" news, and bad news. First, there is a high probability that we'll get to see your hypothesis tested. From a logical extrapolation of current world geo-political trends it seems clear that nuclear detonations will be occurring in the relatively near future. (hint: Iran and their proxies)
The bad news is, those nuclear detonations won't be occurring in unpopulated areas...