Arctic Ocean (AO)
Arctic Ocean (in the USSR, by the ruling of the USSR Central Executive Committee dated June 27, 1935, it was replaced by the name “Severnyi Ledovityi Okean” or the “Northern Ice Ocean”) – the smallest ocean on the planet. Its area is 14.75 million km2 (around 2.8 % of the World Ocean area); the volume is around 18 million km3. The average depth is 1,225 m and the maximum depth is 5,527 m. It washes northern coasts of Eurasia and North America. By physiogeographic features, AO is divided into three large parts: the Arctic Basin, central deepwater part of the ocean, limited by the edge of the continental shelf; the North European Basin – the Greenland Sea, the Norwegian Sea, the Barents Sea, and the White Sea; and marginal Arctic seas – all the other seas, straits, and the Hudson Bay. The Arctic Basin is subdivided into two subbasins: Eurasian and Amerasian, with the borderline along the submerged Lomonosov Ridge. The Kara Sea, the Laptev Sea, the East Siberian Sea, and the Chukchi Sea are often called the Siberian shelf seas in the Russian science. In other countries the ocean is called the Arctic Ocean. The AO is rich in islands: Greenland (the largest island of the World Ocean), the Canada Arctic Archipelago, Shpitsbergen, Franz Josef Land, Novaya Zemlya, Severnaya Zemlya, the New Siberian Islands, the Wrangel Island, etc.; the total area is around 4 million km2.
Large rivers that flow into AO are: the Northern Dvina, the Pechora, the Ob, the Taz, the Yenisei, the Khatanga, the Olenyok, the Lena, the Yana, the Indigirka, the Kolyma, the Mackenzie, etc. The coastline of AO is quite complicated; it forms a number of seas and bays. Shoreline features are diverse. The shores of Greenland, Iceland, the Scandinavian Peninsula are mostly rocky and high, with fjords; the shores of the Canada Arctic Archipelago are rocky but not high. The northern shore of Asia is mostly abrasive and high, though sometimes it can be low and smooth, including delta coasts and lagoon coasts, etc.
AO bottom relief is characterized by well-developed shelf area, steep continental slope, and huge submerged ridges in the Arctic Basin. The width of the shelf zone can reach 1,200–1,300 km (near the New Siberian Islands, the Canada Arctic Archipelago). All the seas of AO are within the shelf zone (except of the Greenland Sea and the Norwegian Sea, straits, and the Hudson Bay). More than a half of AO area, namely, 8.11 million km2, is less than 500 m in depth, while the depths over 4,000 m are only 0.32 million km2 (2.2 % of the area). There are trans-oceanic submerged ridges such as the Lomonosov Ridge, the Mendeleev-Alfa Ridge, the Gakkel Ridge, and other elevations that are part the Arctic Basin into deep basins including the Nansen Basin, the Amundsen Basin, the Makarov Basin, the Podvodnikov Basin, the Canada Basin, etc. Relatively high Lomonosov Ridge over the basins’ bottom can reach 3,300–3,700 m. Minimal depth over the Lomonosov Ridge is 954 m. Floor sediments in AO (in the shelf zone) are terrigenous – sand, sandy silt, and organic and nonorganic silt in the deep water.
Climate, hydrological, and ice conditions of AO are determined specifically by its high-latitude location, atmospheric circulation, water, and heat exchange with the Atlantic and Pacific Oceans, and large continental water supply. The high-latitudinal location of AO – almost all of it is within the Polar Circle – determines the existence of polar day and polar night. Little sun in the winter period in combination with the strong reflecting capacity of snow and ice cover (5–10 times higher than the reflecting capacity of water) leads to year-round ice, harsh climate, and considerable interseasonal (from winter to summer and from summer to winter) changes in hydrometeorological conditions. Atmospheric circulation has a most significant effect over natural processes in AO. It is in the atmosphere where principal advection (inflow) of heat to the Arctic happens, and surface winds largely determine the circulation of water and ice in the ocean.
During water exchange a great amount of warm and salty Atlantic and Pacific waters flow into AO. Water from the Atlantic is brought mainly by North Atlantic Current through Faroe-Shetland Channel – on average 126 × 1012 m3 a year, bringing 41 × 102 J of warmth and 44.3 × 1014 kg of salt. To the north from Spitsbergen, the Atlantic waters arriving there with West Spitsbergen Current submerge under the less dense Arctic waters and turn into warm deepwater current (with the temperature above 0 °C) in the Arctic Basin. Due to the Atlantic waters, air temperature in this polar region is 8–10 °C higher than on the New Siberian Islands located 200 km to the North. Waters from the Pacific Ocean come to AO through the Bering Strait in the amount of 30 × 1012 m3 a year on average. Around 5.14 × 1012 m3 of fresh water from the mainland flows into AO a year. These waters accelerate the process of ice formation and, creating discharge currents, facilitate ice removal from the ocean.
Characteristic features of AO’s climate are mostly harsh continental conditions, cloudy weather, and fogs in summer, low air temperatures, strong winds, and snowstorms in winter. The average monthly air temperature is from −2 °C in the southern part of the Norwegian Sea to −36 °C in the region of the Canada Arctic Archipelago, around −30 °C in the seas of the Siberian Shelf; in summer it is up to 10–12 °C in the Norwegian Sea and 4–6 °C in the seas of the Siberian Shelf. In winter the minimum surface temperature of the air over the Arctic Basin, the Canada Arctic Archipelago, and the Kara and the Laptev Seas can reach −53 °C. In summer maximum air temperature in the coastal areas of the Siberian Shelf seas is up to 28 °C, with up to 15 °C in the north.
Average speed of wind: in winter over the North European Basin, the average speed of wind is 9–10 m/s; in the seas of the Siberian Shelf, it is 5–10 m/s; in the Arctic Basin, it is up to 5 m/s; and in the summer, it does not exceed 5 m/s. Storms (wind speed over 15 m/s) happen mostly in summer. For the Siberian Shelf seas, monsoon changeability of winds is characteristic: in winter prevailing are the winds of south direction, blowing from land to water; in summer, winds of north direction, blowing from sea to land.
The ice of AO is its major physiographical feature. It has a huge impact over environment and human activity not only in the high, but also in the middle latitudes of the Northern hemisphere. The main currents of AO are as follows: Eastern Anticyclonic Circulation (velocity 2–5 cm/s), Trans-Arctic Current (2–10 cm/s), East Greenland Current (around 20 cm/s in Fram Strait, around 40 cm/s southward of Iceland), Norwegian (30–40 cm/s), West Spitsbergen (20–30 cm/s), Nordcape (10–30 cm/s), and Pacific (speed around 40 cm/s, in summer). Trans-Arctic and East Greenland Currents drive ice and cold Arctic waters of AO. Warm and salty waters from the Atlantic brought by Norwegian and West Spitsbergen currents in the area northward off Spitsbergen go to the depth and form in the Arctic Basin a very weak deep current in the layer around 200–1,000 m deep. AO water masses are formed basically by Arctic and Atlantic waters, and, in a lesser extent, by Pacific waters and fresh waters from the mainland.
One of the conspicuous features of the North European Basin of the Arctic Ocean is sharp contrasts of temperature and salinity of waters in the upper layers where warm and more salty Atlantic waters brought northward by the Norwegian Current meet cold and less salty Arctic waters driven southward by the East Greenland Current. In the contact area hydrologic fronts are formed, the most lengthy, intense, and sustainable in the World Ocean. The fronts cause drastic weather changes, frequent fogs, large accumulations of nutritional substances, and, consequently, of plankton and fish.
Weather conditions in Siberian Shelf marginal seas are harsh. The seas are covered with ice for the most part of the year. At this time the water in them is almost homogenous from surface to bottom, with the water temperature close to the freezing temperature. In summer the water gets warm only in a relatively narrow coastal stripe, free from ice during 1–3 months a year (in some areas of seas this happens not every year). Water temperature in summer in the shorefront, heavily influenced by river discharge, can reach 8–10 °C; to the north it gets colder to make 0 °C near the ice edge. Water salinity in summer in the shoreline area is not higher than 10‰, to the north it rises up to 30–32‰ near the ice edge.