On January 21, 1968, a U. S. Air Force B-52G Stratofortress was flying a secret Airborne Alert mission over Baffin Bay, loaded with four thermonuclear weapons.
The mission, known as Operation Chrome Dome, was designed to keep nuclear-armed bombers constantly in the air near the Soviet border. However, an in-flight cabin fire filled the cockpit with smoke, forcing the crew to abandon ship. The unmanned bomber crashed onto the sea ice in North Star Bay, Greenland, just seven miles from Thule Air Base.
The high-explosive components of the four B28 thermonuclear bombs detonated on impact without triggering a nuclear explosion. Burning jet fuel melted a massive hole in the ice, sending radioactive plutonium and bomb wreckage plunging into the freezing ocean below. The military launched a massive, top-secret cleanup effort named Operation Crested Ice.
Hundreds of American and Danish workers labored in sub-zero temperatures and polar darkness to scrape up millions of gallons of contaminated ice and debris. While official U. S.
government reports maintained that all four nuclear weapons were destroyed and accounted for, a 2008 BBC investigation based on declassified documents raised a chilling alternative. Declassified records revealed that military officials realized only three bombs worth of material had been recovered. A covert search using a Star III miniature submarine failed to locate the second stage of the fourth weapon, carrying serial number 78252.
Fearing political backlash from Denmark, which banned nuclear weapons on its territory, the Pentagon quietly abandoned the search, leaving the remains of a thermonuclear weapon buried somewhere beneath the Arctic seabed.