Current global warming has a significant impact on the climate systems of the ocean and atmosphere, causing a restructuring of large-scale planetary processes, atmospheric and oceanic circulation and complex changes in the characteristics of the natural environment. Under these conditions, accumulation of excess heat and its redistribution in the ocean water column, accelerated changes in salinity on the sea surface and in the water column, caused by the intensification of the global water (hydrological) cycle, are observed. The observed climate response includes an increase in the frequency, intensity and magnitude of the impacts extreme temperatures, marine heat waves (MHWs), heavy precipitation, droughts and tropical cyclones on various natural ecosystems and economic sectors.

Using climate data from the National Oceanic and Atmospheric Administration (USA), Roshydromet,  and atmospheric reanalysis from the European Weather Forecast Center, trends and regional features of  interannual changes in water and air temperature, heat content, salinity, and salt content of waters in the Pacific  subarctic, Far Eastern seas, East Asian seas, and the Pacific and Indian oceans over the past 4 decades have  been determined. An analysis of the three-dimensional structure of trends in hydrological characteristics and  cause-and-effect relationships between the conditions of their formation and large-scale and regional processes  in the ocean and atmosphere has been performed.  

In the last 4 decades the highest warming rate within the study area was observed in the extratropical zone  of the NW Pacific, and contribution of the trend to the total variance of the average annual sea surface  temperature reached 30–40%. Trends in temperature and salinity change vary significantly across layers and  climate zones. In the last two decades, in the subarctic waters of NW Pacific increase in the heat content of the  upper 1000-meter layer by ~3% was accompanied by a statistically significant decrease in the salinity of this  layer. In the NE Pacific, there was an increase in the heat content of this layer by ~2%, accompanied by a  statistically insignificant decrease in salinity.  

Changes in the characteristics of the marine heat waves show significant positive trends and confirm a  steady increase in these phenomena in terms of the frequency of events, their duration, intensity and integral  indicators, emphasizing significant regional differences in these indicators over the past decades. Statistically  significant correlations were revealed between fluctuations in various MHWs indicators and changes in the  characteristics of surface air temperature anomalies, the height of the geopotential of the 500 mb isobaric  surface, and climate indices.