Arctic Ocean deepest point is Litke Deep in the Eurasian Basin, at . The two major basins are further subdivided by ridges into the Canada Basin (between Alaska/Canada and the Alpha Ridge), Makarov Basin (between the Alpha and Lomonosov Ridges), Amundsen Basin (between Lomonosov and Gakkel ridges), and Nansen Basin (between the Gakkel Ridge and the continental shelf that includes the Franz Josef Land). In large parts of the Arctic Ocean, the top layer (about ) is of lower salinity and lower temperature than the rest. It remains relatively stable, because the salinity effect on density is bigger than the temperature effect.
Nansen (lunar crater) lies across the northern rim of Nansen, and a similar formation is located along the inner southern wall. A merged chain of tiny craters lies across the eastern rim. The interior floor of Nansen is more hummocky and irregular in the northern half, while the southern part of the floor is relatively level. There is a small, bowl-shaped crater in the southeastern part of the floor, and many tiny craterlets lie across the interior and along the inner walls. By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that