The Sea of Azov (Азо́вское мо́ре - Azovskoye more; Азо́вське мо́ре - Azovs'ke more, ) is the world's shallowest sea, linked by the Strait of Kerch to the Black Sea to the south. It is bounded on the north by Ukraine, on the east by Russia and on the west by the Crimean peninsula. The Don River flows into it.
The current name is popularly said to come from a certain Polovtsian prince named Azum or Asuf, who was killed defending a town in this region in 1067. Most scholars derive the name from the city of Azov, or Azak, meaning "low" in Turkish, a reference to its location.
The Sea of Azov is the shallowest sea in the world with an average depth of and maximum depth of ; where silt has built up, such as the Gulf of Taganrog, the average depth is less than . The prevailing current in the sea is a counter-clockwise swirl. Salinity varies from 1 to 15 parts per thousand (compared to 30 to 40 for the oceans) across the sea and with season.
The shallowness and low salinity of the sea make it vulnerable to freezing during winter. Formation of sea ice can occur temporarily at any time from late December to mid-March. Under the present climate, the sea no longer freezes over, although during the 18th and 19th centuries and as far as the late 1970s, it was normally frozen over every year by early February.
The current vertical profile of the Sea of Azov exhibits oxygenated surface waters and anoxic bottom waters, with the anoxic waters forming in a layer 0.5 - 4 m in thickness. The occurrence of the anoxic layer is attributed to seasonal eutrophication events associated with increased sedimantary input from the Don and Kuban Rivers. This sedimentary input stimulates biotic activity in the surfaces layers, which photosynthesize under aerobic conditions. Once expired, the dead organic matter sinks to the bottom of the sea where bacteria and microorganisms, using all available oxygen, consume the organic matter, leading to anoxic conditions. Studies have shown that in the Sea of Azov, the exact vertical structure is dependent on wind strength and sea surface temperature, but typically a 'stagnation zone' lies between the oxic and anoxic layers.