Nuclear submarine nuclear-powered submarine was first proposed in the United States Navy by the Naval Research Laboratory's Ross Gunn in 1939. Construction of the world's first nuclear powered submarine was made possible by the successful development of a nuclear propulsion plant by a group of scientists and engineers at the Naval Reactors Branch of the Bureau of Ships and the Atomic Energy Commission. In July 1951 the U.S. Congress authorized construction of the first nuclear-powered submarine, "Nautilus", under the leadership of Captain Hyman G. Rickover, USN (sharing names with Captain Nemo's fictional submarine in Jules Verne's "Twenty Thousand Leagues Under the Sea",
North Pole will be entirely free of ice in the summer. This may have significant commercial implications; see "Territorial Claims," below. The retreat of the Arctic sea ice will accelerate global warming, as less ice cover reflects less solar radiation, and may have serious climate implications by contributing to Arctic cyclone generation. Polar bears are believed to travel rarely beyond about 82° North owing to the scarcity of food, though tracks have been seen in the vicinity of the North Pole, and a 2006 expedition reported sighting a polar bear just from the Pole. The ringed seal has also been seen at