Reports the BBC : http://news.bbc.co.uk/1/hi/world/europe/7720049.stm
BBC wrote:
The United States abandoned a nuclear weapon beneath the ice in northern Greenland following a crash in 1968, a BBC investigation has found.
The view was that no-one else would be able covertly to acquire the sensitive pieces and that the radioactive material would dissolve in such a large body of water, making it harmless.
Other officials who have seen classified files on the accident confirmed the abandonment of a weapon.

Small hourglass island
Always raining and foggy
Use an umbrella
Always raining and foggy
Use an umbrella