Seasonal and Interannual Variability of Oceanographic Conditions in the Southwestern Part of the Sea of Okhotsk

G. V. Shevchenko and V. N. Chastikov

The seasonal variability of oceanographic conditions in the southern part of the Sea of Okhotsk is described based on long-term mean temperature T and salinity S from observations along a standard oceanographic section Cape Aniva–Cape Dokuchaev (May–November). It is shown that the Soya Current is relatively weak in spring, with low temperature and salinity gradients along the section. The Sea of Okhotsk low-salinity water mass is observed in the upper layer. It was formed as a result of melting of a large amount of ice brought here with the East Sakhalin Current from the northwestern part of the Sea of Okhotsk. A cold intermediate layer (CIL) at depths of 50–150 m extends along the entire section. The cold intermediate layer core with a temperature at the edge of the Sakhalin shelf of about –1.3°C is retained during a period of maximum warming in August; however, in October–November the intensified flow of the East Sakhalin Current (up to 50 cm/s) results in a situation when relatively warm low-salinity waters, connected with the Amur River runoff, dissipate CIL. The results of 12 surveys conducted by the Sakhalin Research Institute for Fisheries and Oceanography in 1998–2004 show significant deviations of T and S [10] in different years from the calculated values. Generally, maximum anomalies (_T > 4°C and _S > 0.55‰) are observed in the surface layer. Their values and statistical significance decrease with depth. However, the situation is opposite in some cases. The maximum deviation from normal was observed in June 1999, when warm and salt waters were located much further seaward from the Kunashir shelf, which is most likely connected with the Soya Current meandering.