Purpose. The study is purposed at determining trends and regional features of interannual changes in salinity and salt content in the upper 1000-m layer of extratropical zone in the northwestern Pacific Ocean and at analyzing their possible cause-and-effect relations with large-scale and regional processes in the ocean and atmosphere over the last two decades of the current period of global warming.

Methods and Results. The study is based on NOAA climate data sets on salinity and current velocity in the nodes of the 0.3 × 1º regular grid at 31 levels for 2000–2022 derived from the oceanographic observation system GODAS (NCEP Global Ocean Data Assimilation System), as well as the series both of climate indices from the NOAA websites and routine salinity observations performed at the Rosgidromet coastal hydrometeorological stations. Besides, average monthly ERA5 reanalysis data on precipitation (Reanalysis Data ERA5 monthly 2d Surface) and evaporation from the underlying surface (WHOI OAFlux version3 monthly evapr oaflux) obtained from the NOAA Oceanographic Data Access ERDDAP server were applied. The process of analyzing involved the methods of cluster, correlation and regression analysis, as well as the apparatus of empirical orthogonal functions. The conducted research made it possible to identify and characterize the regional spatial and temporal features of the accelerated changes in salinity and salt content in the upper 1000-m water column of the studied area under conditions of the current warming phase accompanied by the intensification of global and local hydrological cycles. The quantitative characteristics of the noted trends and their statistical significance were assessed.

Conclusions. On the whole, a tendency towards a gradual decrease in average salinity near the sea surface and water desalination in the upper 1000-m layer accompanied by an increase of water heat content in this layer by 3% is observed over the water area under study.