Typical variability of oceanographic fields in the cold intermediate layer and its influence on the water dynamics in the Okhotsk Sea

Spatial variability of temperature and salinity in the cold intermediate layer and water circulation in the Okhotsk Sea are considered for typical cold and warm conditions of the spring season (May-June) determined by separate averaging of all available data of oceanographic observations and diagnostic modeling. The «cold» and «warm» years were separated following to the typization proposed by V.A. Luchin and V.I. Matveev [2016]. The total area with water temperature below 0 ^oC is evaluated for both types. The difference of water temperature between the types reaches 1 ^oС on the depths of 30 and 90 m in certain parts of the sea, but decreases to 0.5 ^oС at the lower boundary of the cold layer. The northward (West Kamchatka Current) and northwestward (Middle Okhotsk Sea flow) transport of the warm and salty transformed North Pacific Intermediate water prevails for the «warm» type, as could be seen from spatial distribution of temperature and salinity in the above cold subsurface layer and the isolines patterns. Water density in the cold layer generally increases toward the northern and northwestern coasts of the sea where it is significantly higher in springs of «cold» years than in «warm» years. The density increases in the southern part of the sea, too, but without such difference between the types because of advective nature of this pattern. The major water gyres vary in size and intensity between the types, in particular, the anticyclonic gyre over the deep-water Kuril Basin is more intense in cold springs. The North Okhotsk Current, flowing westward along the northern shore, turns to the south at 144^o E in springs of the cold type. Besides, another alongshore current appears under cold conditions that flows from the Shantar Islands to northern Sakhalin Island and blocks the Amur River outflow to the Okhotsk Sea. On the contrary, in springs of the warm type, the outflow of freshened water from the Amur to the north reaches the latitude of 56.5^o N, then turns to the south and replenishes the East Sakhalin Current.

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