Barents Sea  The Barents Sea ( , also ; , ; ) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters. Known among Russians in the Middle Ages as the Murman Sea ("Norwegian Sea"), the current name of the sea is after the historical Dutch navigator Willem Barentsz. This is a rather shallow shelf sea, with an average depth of , and it is an important site for both fishing and hydrocarbon exploration. The Barents Sea is bordered by the Kola Peninsula to the south, the shelf edge towards the Norwegian Sea to the west, and the archipelagos of Svalbard to the northwest, Franz Josef Land to the northeast and Novaya Zemlya to the east. The islands of Novaya Zemlya, an extension of the northern end of the Ural Mountains, separate the Barents Sea from the Kara Sea. Although part of the Arctic Ocean, the Barents Sea has been characterised as "turning into the Atlantic" because of its status as "the Arctic warming hot spot." Hydrologic changes due to global warming have led to a reduction in sea ice and in stratification of the water column, which could produce major changes in weather in Eurasia. The southern half of the Barents Sea, including the ports of Murmansk (Russia) and Vardø (Norway) remain ice-free year round due to the warm North Atlantic drift. In September, the entire Barents Sea is more or less completely ice-free. Until the Winter War (1939–40), Finland's territory also reached to the Barents Sea. Its harbor at Petsamo was Finland's only ice-free winter harbor. There are three main types of water masses in the Barents Sea: Warm, salty Atlantic water (temperature >3 °C, salinity >35) from the North Atlantic drift; cold Arctic water (temperature <0 °C, salinity <35) from the north; and warm, but not very salty, coastal water (temperature >3 °C, salinity <34.7). Between the Atlantic and Polar waters, a front called the Polar Front is formed. In the western parts of the sea (close to Bear Island), this front is determined by the bottom topography and is therefore relatively sharp and stable from year to year, while in the east (towards Novaya Zemlya), it can be quite diffuse and its position can vary markedly between years.