Temporaland Spatial Variation Of Salinity In The Pacific Ocean And Climatic Effects

In recent years,under the trend of global warming,the global water cycle has intensified.And global warming and the hydrological cycle can be shown by long-term changes in ocean salinity.The variation of the sea surface salinity maximum(SSS-max)is an important indicator of the global water cycle,ocean advection and mixing process.The ocean plays a leading role in the global water cycle,and the tropical Western Pacific plays a very important role in global circulation and climate change due to its complex circulation and water mass distribution.The Pacific Decadal Oscillation(PDO)is a Pacific climate mode with a long cycle.As a common climate index,PDO plays an important role in the climate change of the Pacific Ocean and its surrounding areas.Current studies on salinity in the Pacific Ocean mostly focus on mesosphere and sub-surface.Based on the hydrological data,the variation trend of salinity from seasonal to interannual changes in the short period of time was studied.However,there are few studies on the surface salinity of the Pacific Ocean,especially the SSS-max.The Decadal variation and mechanism of the SSS-max in the Pacific ocean and its relationship and interaction with The(PDO)are not clear.In this paper,two sets of salinity data,EN4 data from 1999 to 2020 and Argo data from 2004 to 2020,are used to study the interdecadal variation of the SSS-max in the South and north Pacific Ocean and the inter-decadal variation of tropical water in the South and north Pacific at sections 165°E and 137°E,and their relationship with the PDO.The factors affecting the interdecadal variation of the SSS-max in the North and South Pacific are proved by the analysis of the salinity budget.and the factors influencing the interdecadal variation of the SSS-max in the south and north Pacific Ocean are proved by the analysis of the salinity budget.The analysis results of the two sets of data show that the SSS-max of the South Pacific mainly moves in the north-south swing,and its central position moved to the northernmost end in 2004 and2016,and to the southernmost end in 2000 and 2011.The SSS-max in the South Pacific is synchronized with the PDO,when the PDO is in positive(negative)phase,the SSS-max in the South Pacific is north(south).The SSS-max in the North Pacific is mainly characterized by changes in its salinity values,which were lower in 2004 and 2019 and higher in 2013 / 2014.While the SSS-max in the North Pacific lags behind the PDO for about 2 years.Specifically,when the PDO is in positive(negative)phase,the SSS-max in the North Pacific is small(large).The salinity budget analysis,the variations of the SSS-max in the North and South Pacific show the meridional advection plays a dominant role.By analyzing the interdecadal variation of the subsurface layer and its relationship with PDO,the results show that the main variation of South Pacific Tropical Water at section 165°E is the up-down fluctuation,which is synchronous with PDO.When the PDO index is positive(negative)and the south pacific SSS-max sinks westward to the165°E section,the South Pacific Tropical Water center is shallower(deep).The main variation of the north Pacific tropical water at 137°E section is the change of salinity value,which lags behind PDO by two years.When the PDO index is positive(negative)and the north pacific SSS-max dives westward to the 137°E section,the salinity of North Pacific Tropical Water is smaller(larger).In this paper,the decadal variation trend of the SSS-max and the section165°E and137°E of the Pacific Ocean in recent 20 years has been analyzed in detail,and it is found that there is a strong correlation between the time series and PDO.However,the mechanism of synchronization or lag between PDO and PDO needs further study.