SEASONAL VARIABILITY OF OCEANOLOGICAL CONDITIONS ON THE NORTHEASTERN SAKHALIN SHELF BASED ON THE SURVEYS ON STANDARD SECTIONS

Abstract

The long-term mean temperature and salinity distributions on 5 standard oceanological sections on the northeast shelf of Sakhalin were analyzed for 4 months of the navigation period (July-October) including a radical restructuring of hydrological conditions in the transition from summer to autumn. The data of soundings performed during the pollock ichthyoplankton surveys were used to study oceanological conditions in June. The low salinity water formed by the Amur River runoff are shown to appear on the northeastern shelf in the first half of June after the heavy ice breaking in the southern Sakhalin Bay. Low salinity water and ice are pushed off toward the deep sea under the influence of the southern winds typical for a warm season, and an oceanological front is formed near the 52°N. This front prevents the low-salinity water from flowing southward until the second half of September, when changes into a winter monsoon with the prevailing northerly winds take place. This promotes destruction of hydrological front and deepening of the cold intermediate water layer. The waters with the 4–6°C temperature and salinity of about 31 psu occur at the shelf edge along the northeastern Sakhalin coast. A powerful stream with the relatively warm low salinity water is being formed along the shore that reaches the southeastern part of Sakhalin and northern coasts of Hokkaido Island.