The American Navy is mapping out the sea bed of the Arctic Circle to try and decide which country has sovereignty over what. With a quarter of the world's undiscovered oil, natural gas and other minerals thought to lie beneath its frozen waters, countries are falling over themselves to claim territory there. Things have now become so tense that the Norwegian government have called for an end to the Arctic land grab race. Our correspondent Mike Thompson reported from the island Spitsbergen deep within the Arctic Circle.