The Kara Sea is part of the Arctic Ocean north of Siberia. It is separated from the Barents Sea to the west by the Kara Strait and Novaya Zemlya, and the Laptev Sea to the east by the Severnaya Zemlya archipelago. It is named for the Kara River (flowing into Baydaratskaya Bay), which is now relatively insignificant but which played an important role in the Russian conquest of northern Siberia. The Kara Sea's northern limit is marked geographically by a line running from Cape Kohlsaat in Graham Bell Island, Franz Josef Land, to Cape Molotov (Arctic Cape), the northernmost point of Komsomolets Island in Severnaya Zemlya. The Kara Sea is roughly 1,450 kilometres long and 970 kilometres wide with an area of around 880,000 km2 (339,770 sq mi) and a mean depth of 110 metres (360 ft). Compared to the Barents Sea, which receives relatively warm currents from the Atlantic, the Kara Sea is much colder, remaining frozen for over nine months a year. The Kara receives a large amount of freshwater from the Ob, Yenisei, Pyasina, and Taimyra rivers, so its salinity is variable. Its main ports are Novy Port and Dikson and it is important as a fishing ground although the sea is ice-bound for all but two months of the year. Significant discoveries of petroleum and natural gas, an extension of the West Siberian Oil Basin, have been made but have not yet been developed.