And a bit more info to ponder. The extent of change in the Arctic polar ice was not recorded prior to the mid 1970's or so. Before that there is no consistent data. Roughly 50 years? That is not even a thousandth of a blink in time. Prior we simply don't know how many times, if any, the passage could have been made. I would bet the U.S. Navy and the U.S. Air Force knows, post WWII but hey, who would ask them? Further, would they tell?

Chief