History of submarines few years before the US, and paralleled subsequent US development in this area. In the 1950s, nuclear power partially replaced diesel-electric propulsion. The sailing of the first nuclear-powered submarine, the USN ""Nautilus"" in 1955 was soon followed by similar British, French and Russian boats. Equipment was also developed to extract oxygen from sea water. These two innovations, together with inertial navigation systems, gave submarines the ability to remain submerged for weeks or months, and enabled previously impossible voyages such as the crossing of the North Pole beneath the Arctic ice cap by the USS "Nautilus" in 1958. Most of the
Ice cap climate polar and there are some communities that are situated in a transitional zone between the two climates, but barely qualify as a tundra. Some places like Antarctica had a different climate before having an ice cap climate. Under the Köppen climate classification, the ice cap climate is denoted as "EF". Ice caps are defined as a climate with no months above . Such areas are found around the north and south pole, and on the top of the highest mountains. Since the temperature never exceeds the melting point of ice, any snow or ice that accumulates remains there permanently, over