Mean climatic parameters of the upper mixed layer in the Bering Sea (lower boundary, temperature, salinity) and their annual variability
All available deep-water oceanographic data obtained in the Bering Sea in 1929-2019 are analyzed (101,425 oceanographic stations). Lower boundary of the upper mixed layer is determined from the vertical temperature profiles using the criterion of temperature deflection from SST (10 % for June-October and 0.2, 0.3, and 0.5 oС for November-May). The mixed layer is rather thin in June-September, its thickness is 10-20 m over the major part of the sea, and 30-40 m at the straits between central Aleutian Islands. In December-March, the mixed layer depth increases to 120-160 m in the northern deep-water sea and up to 180-200 m at the straits between central and eastern Aleutian Islands, though it is thinner in plumes of warm waters entering from the Pacific. At the continental shelf, the mixed layer can be traced to the depth of 20-40 m in the eastern Bering Sea and 60-80 m at Kamchatka in December-January and to 60-80 m in the eastern Bering Sea and 80-100 m at Kamchatka in February-March. The mixed layer temperature distribution is distinguished by two completely different seasonal patterns. The winter distribution pattern with the highest temperature in the areas adjacent to the Aleutian Straits is typical for November-June. The summer pattern with high temperature in the Karaginsky Bay, Bristol Bay, and Norton Sound and lower temperature near the Aleutian Straits is typical for July-October. On the contrary, the salinity distribution pattern is stable, with the highest salinity at the central and eastern Aleutian Straits and lower salinity in the coastal zone as the Anadyr Bay and Norton Sound influenced by the river runoff.