Recently declassified US documents reveal a disturbing and thankfully unequaled incident during the cold war.
Thule Air Base in northerly Greenland has been of great tactical significance to the US ever since it was created in the early 1950s, enabling a radar to survey the skies for missiles approaching from the North Pole. The US government believed the Soviet Union would destroy the base as an opener to a nuclear strike against the US. Persuant to this, the 1960's saw the US undertake the aptly titled 'Chrome Dome' missions in an endeavor to provide a viable deterrent. This deterrent took the form of B52 bombers armed with several nuclear explosive devices routing over the territory being able to navigate immediately to the Russian capital Moscow, to deploy their payload should the Soviet Union strike the base at Thule.
However, the plan did not work out quite as smoothly as they had anticipated.
In late January 1968, one of these missions ended in near disaster when a B52 bomber carrying four nuclear armed explosives caught fire and crashed onto the ice several miles from the Thule base. The pilots recount that a fire was reported in the cockpit which quickly spread to other sections of the plane making a scheduled and safe landing impossible. A few minutes after the fire broke out the two pilots and four crew members took the decision to eject themselves from the stricken aircraft before it crashed into millions of pieces on the ice below.
Following the crash, military personnel, local Greenlanders and Danish workers rushed to clean up the debris and to retrieve the nuclear explosives. Unfortunately, only the US military personnel were aware of the existence of nuclear materials meaning the local islanders were not wearing any protective clothing during the clean up exercise. Upon hitting the ice during the crash, the four nuclear devices detonated but given the bombs were not armed the nuclear triggers did not function and simply broke up along with the rest of the wreckage. Millions of gallons of ice were taken from the crash site from which the US government later confirmed that all the explosives had been 'destroyed'.
This is where the story somewhat darkens. The US sources were technically correct in their statement around the bombs being 'destroyed' however, what was not revealed at the time was that only 3 devices had been accounted for from analysis of the debris. Documents reveal that officials concluded that one of the devices must have become extremely hot during the crash and melted through the ice into the freezing waters below.
A rescue mission was then launched (without the knowledge of the Danish authorities) to recover the missing device. In April 1968 a US submarine was dispatched to the area. The underwater search was beset by technical problems and, as winter encroached and the ice began to freeze over the search was abandoned. The US papers reveal that they held the opinion that if the weight of the US military could not locate the device it would be extremely unlikely that any other country could either and therefore, no further searches for the device were undertaken.
For what of the consequences of leaving a nuclear device sitting in the ocean? The declassified papers reveal that scientists believed the radioactive material would simply dissolve in such a large body of water, making it harmless....