North Pole Since 2002, the Russians have also annually established a base, Barneo, close to the Pole. This operates for a few weeks during early spring. Studies in the 2000s predicted that the North Pole may become seasonally ice-free because of Arctic ice shrinkage, with timescales varying from 2016 to the late 21st century or later. The sea depth at the North Pole has been measured at by the Russian Mir submersible in 2007 and at 4,087 m (13,410 ft) by USS "Nautilus" in 1958. The nearest land is usually said to be Kaffeklubben Island, off the northern coast of Greenland about
Voyage to the Bottom of the Sea Wilkins. Calvert wrote the book "Surface at the Pole" about this and the other Arctic missions of USS "Skate." The film "Voyage to the Bottom of the Sea" begins with "Seaview" in the Arctic for the final phase of her sea trials, including a dive under the ice cap. Two milestones in underwater exploration were achieved in 1960, the year before "Voyage to the Bottom of the Sea" was released. On January 23, 1960, Jacques Piccard and Lieutenant Don Walsh (USN), in the bathyscaphe "Trieste", made the first descent to the bottom of the Challenger Deep. The Challenger Deep is