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
Ice Station Zebra (novel) under the North Pole), , and . MacLean may have been anticipating the excitement of his British readers regarding the upcoming commissioning of the , the Royal Navy's first nuclear submarine. Also, MacLean may have been influenced by press reports about the nuclear-powered submarine USS "Skate" visiting Ice Station "Alpha", located on Ice Island T-3 in the Arctic, on 14 August 1958, as part of the International Geophysical Year (IGY)". At the time that the novel was published, under-the-ice operations by US Navy nuclear-powered submarines were prohibited until SUBSAFE measures had been implemented following the loss of the . "Ice