The East Siberian Sea is less than 20m deep in the western part and around 40m deep in the eastern reaches, as is the Long Strait. The center of the Chukchi Sea is only 50m deep, with gentle variation in depth. The Bering Strait is home to two islands, Big Diomede (Ratmanov) and Little Diomede Islands; the seas around these islands are 60m deep to the east and 50m deep to the west.
These straits constrain the movement of seawater and sea ice. The tides that overlie the ocean currents move about dramatically. The accumulation of multi-year ice often causes the formation of local ice massifs.
3.3.2 Low-salinity Water
The NSR coast is nourished by freshwater from the rivers that flow into the Arctic Ocean from the Eurasian continent. As a result, the coastal seas such as the Kara Sea, which is fed by the Ob and Yenisey Rivers; the Laptev Sea, which is fed by the Lena; and the East Siberian Sea, into which the Indigirka and Kolyma rivers flow, form a broad coastal region of low-salinity sea.
Temperature-density-salinity diagram of sea water (Ono, 1996)
The density of seawater is dependent on its temperature and salinity. Salinity is measured in weight per mil, meaning weight of salt in grams for every kilogram of seawater. Fresh water, which has a salinity of 0%, reaches its maximum density at 4℃; at 0℃, it freezes. As salinity increases, both the temperature of maximum density (Tρmax) and the freezing point (Tf) decrease. However, the temperature of maximum density drops faster, so that the two intersect at a salinity of 2.47%. As the fresh water in lakes and rivers cools during the autumn and winter months, the cooled water grows heavy and sinks, creating convection currents. At 4℃ and lower, however, the water is too light to sink, forming layers without convection, so that only the lake surface is cooled and freezes over. Since seawater has a salinity of 3.3-3.5%, convection continues until the freezing point is reached.
Distribution of low-salinity seawater in the NSR (2.5% or less. Thick lines: winter; thin lines: summer) (Ono, 1996)