Arctic Ocean gas reserves, and the Chukchi shelf forms the border between Russian and the United States as stated in the USSR–USA Maritime Boundary Agreement. The whole area is subject to international territorial claims. An underwater ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins: the Eurasian Basin, which is between deep, and the Amerasian Basin (sometimes called the North American, or Hyperborean Basin), which is about deep. The bathymetry of the ocean bottom is marked by fault block ridges, abyssal plains, ocean deeps, and basins. The average depth of the Arctic Ocean is . The
Fridtjof Nansen like a spiral staircase, down towards the depths". In 1909 Nansen combined with Bjørn Helland-Hansen to publish an academic paper, "The Norwegian Sea: its Physical Oceanography", based on the "Michael Sars" voyage of 1900. Nansen had by now retired from polar exploration, the decisive step being his release of "Fram" to fellow Norwegian Roald Amundsen, who was planning a North Pole expedition. When Amundsen made his controversial change of plan and set out for the South Pole, Nansen stood by him. Between 1910 and 1914, Nansen participated in several oceanographic voyages. In 1910, aboard the Norwegian naval vessel "Fridtjof", he