Revealed: How U.S. left nuclear warhead lying at bottom of ocean after B52 crash in 1968
The Pentagon believed the former Soviet Union would destroy the base as a prelude to a nuclear strike against the U.S. and began flying nuclear-armed B52s continuously over Thule in 1960 in order to retaliate.
Thule Air Base has been a major strategic asset to the U.S. since it was built in the early 1950s, as it allowed a radar to scan the skies for missiles fired over the North Pole.
Greenland is a self-governing province of Denmark, but the carrying of nuclear weapons over Danish territory was kept secret, according to the BBC investigation.
On January 21, 1968, one of the missions went wrong and a bomber crashed into the ice a few miles from the air base.
Over the next few months a massive operation took place to recover the debris of the aircraft and collect 500million gallons of ice, some of which contained radioactive wreckage from the bomber.
A declassified U.S. government video, obtained by the BBC, documents the clear-up and gives some ideas of the scale of the operation.
Explosives surrounding the four nuclear warheads had detonated, but had not set off the bombs themselves because they had not been armed by the aircraft crew.
The Pentagon had maintained that all four weapons had been 'destroyed', but declassified documents obtained by the BBC under the U.S. Freedom of Information Act reveal investigators realised only three of the weapons could be accounted for.
One talks of a blackened section of ice which had refrozen with shroud lines from a weapon parachute.
The document reads: 'Speculate something melted through ice such as burning primary or secondary.'
By April, a decision had been taken to send a Star III submarine to the base to look for the lost bomb, which had the serial number 78252, but the Danish government was not informed of the real reason behind the mission.
One document from July reads: 'Fact that this operation includes search for object or missing weapon part is to be treated as confidential NOFORN', the last word meaning not to be disclosed to any foreign country.
It states that the operation should be referred to Danish officials as a survey of the ocean bottom underneath the impact point.
The U.S flew B52s over Iceland continuously as it feared a nuclear attack by Russians
But the underwater search was beset by technical problems and, as winter encroached and the ice began to freeze over, the documents recount something approaching panic setting in.
The abandoned weapons contained uranium and plutonium and could have revealed classified elements of nuclear warhead design. Eventually the search was abandoned, with officials believing the radioactive material would dissolve in such a large body of water, making it harmless.
William H Chambers, a former nuclear weapons designer at the Los Alamos nuclear laboratory, told the BBC: 'There was disappointment in what you might call a failure to return all of the components.
'It would be very difficult for anyone else to recover classified pieces if we couldn't find them.'
A nuclear scientist has told the Daily Mail: 'We really don’t know what has happened to this bomb.
'It’s not going to explode but the possibility remains of very large contamination with all of the dangers that involves.'
11th November 2008